diff --git a/browser/base/content/inspector.js b/browser/base/content/inspector.js
index 6cfda745fda4..58c1a3910f58 100644
--- a/browser/base/content/inspector.js
+++ b/browser/base/content/inspector.js
@@ -549,6 +549,7 @@ IFrameHighlighter.prototype = {
  */
 var InspectorUI = {
   browser: null,
+  tools: {},
   showTextNodesWithWhitespace: false,
   inspecting: false,
   treeLoaded: false,
@@ -883,6 +884,13 @@ var InspectorUI = {
       delete this.domplateUtils;
     }
 
+    this.saveToolState(this.winID);
+    this.toolsDo(function IUI_toolsHide(aTool) {
+      if (aTool.panel) {
+        aTool.panel.hidePopup();
+      }
+    });
+
     this.inspectCmd.setAttribute("checked", false);
     this.browser = this.win = null; // null out references to browser and window
     this.winID = null;
@@ -904,6 +912,7 @@ var InspectorUI = {
    */
   startInspecting: function IUI_startInspecting()
   {
+    document.getElementById("inspector-inspect-toolbutton").checked = true;
     this.attachPageListeners();
     this.inspecting = true;
   },
@@ -918,6 +927,7 @@ var InspectorUI = {
       return;
     }
 
+    document.getElementById("inspector-inspect-toolbutton").checked = false;
     this.detachPageListeners();
     this.inspecting = false;
     if (this.highlighter.node) {
@@ -948,6 +958,11 @@ var InspectorUI = {
       }
       this.ioBox.select(this.selection, true, true, aScroll);
     }
+    this.toolsDo(function IUI_toolsOnSelect(aTool) {
+      if (aTool.panel.state == "open") {
+        aTool.onSelect.apply(aTool.context, [aNode]);
+      }
+    });
   },
 
   /////////////////////////////////////////////////////////////////////////
@@ -1003,6 +1018,7 @@ var InspectorUI = {
             }, INSPECTOR_NOTIFICATIONS.CLOSED, false);
           } else {
             this.openInspectorUI();
+            this.restoreToolState(winID);
           }
         }
 
@@ -1254,7 +1270,113 @@ var InspectorUI = {
     }
     this._log("END TRACE");
   },
-}
+
+  /**
+   * Register an external tool with the inspector.
+   *
+   * aRegObj = {
+   *   id: "toolname",
+   *   context: myTool,
+   *   label: "Button label",
+   *   icon: "chrome://somepath.png",
+   *   tooltiptext: "Button tooltip",
+   *   accesskey: "S",
+   *   onSelect: object.method,
+   *   onShow: object.method,
+   *   onHide: object.method,
+   *   panel: myTool.panel
+   * }
+   *
+   * @param aRegObj
+   */
+  registerTool: function IUI_RegisterTool(aRegObj) {
+    if (this.tools[aRegObj.id]) {
+      return;
+    } else {
+      let id = aRegObj.id;
+      let buttonId = "inspector-" + id + "-toolbutton";
+      aRegObj.buttonId = buttonId;
+
+      aRegObj.panel.addEventListener("popuphiding",
+        function IUI_toolPanelHiding() {
+          btn.setAttribute("checked", "false");
+        }, false);
+      aRegObj.panel.addEventListener("popupshowing",
+        function IUI_toolPanelShowing() {
+          btn.setAttribute("checked", "true");
+        }, false);
+
+      this.tools[id] = aRegObj;
+    }
+
+    let toolbar = document.getElementById("inspector-toolbar");
+    let btn = document.createElement("toolbarbutton");
+    btn.setAttribute("id", aRegObj.buttonId);
+    btn.setAttribute("label", aRegObj.label);
+    btn.setAttribute("tooltiptext", aRegObj.tooltiptext);
+    btn.setAttribute("accesskey", aRegObj.accesskey);
+    btn.setAttribute("class", "toolbarbutton-text");
+    btn.setAttribute("image", aRegObj.icon || "");
+    toolbar.appendChild(btn);
+
+    btn.addEventListener("click",
+      function IUI_ToolButtonClick(aEvent) {
+        if (btn.getAttribute("checked") == "true") {
+          aRegObj.onHide.apply(aRegObj.context);
+        } else {
+          aRegObj.onShow.apply(aRegObj.context, [InspectorUI.selection]);
+          aRegObj.onSelect.apply(aRegObj.context, [InspectorUI.selection]);
+        }
+      }, false);
+  },
+
+/**
+ * Save a list of open tools to the inspector store.
+ *
+ * @param aWinID The ID of the window used to save the associated tools
+ */
+  saveToolState: function IUI_saveToolState(aWinID)
+  {
+    let openTools = {};
+    this.toolsDo(function IUI_toolsSetId(aTool) {
+      if (aTool.panel.state == "open") {
+        openTools[aTool.id] = true;
+      }
+    });
+    InspectorStore.setValue(aWinID, "openTools", openTools);
+  },
+
+/**
+ * Restore tools previously save using saveToolState().
+ *
+ * @param aWinID The ID of the window to which the associated tools are to be
+ *               restored.
+ */
+  restoreToolState: function IUI_restoreToolState(aWinID)
+  {
+    let openTools = InspectorStore.getValue(aWinID, "openTools");
+    InspectorUI.selection = InspectorUI.selection;
+    if (openTools) {
+      this.toolsDo(function IUI_toolsOnShow(aTool) {
+        if (aTool.id in openTools) {
+          aTool.onShow.apply(aTool.context, [InspectorUI.selection]);
+        }
+      });
+    }
+  },
+  
+  /**
+   * Loop through all registered tools and pass each into the provided function
+   *
+   * @param aFunction The function to which each tool is to be passed
+   */
+  toolsDo: function IUI_toolsDo(aFunction)
+  {
+    for each (let tool in this.tools) {
+      aFunction(tool);
+    }
+  },
+};
 
 /**
  * The Inspector store is used for storing data specific to each tab window.
@@ -1389,4 +1511,3 @@ var InspectorStore = {
 XPCOMUtils.defineLazyGetter(InspectorUI, "inspectCmd", function () {
   return document.getElementById("Tools:Inspect");
 });
-
diff --git a/browser/base/content/test/inspector/Makefile.in b/browser/base/content/test/inspector/Makefile.in
index 00905f99673a..2d7537c6b012 100644
--- a/browser/base/content/test/inspector/Makefile.in
+++ b/browser/base/content/test/inspector/Makefile.in
@@ -54,6 +54,7 @@ _BROWSER_FILES = \
 		browser_inspector_treePanel_output.js \
 		browser_inspector_treePanel_input.html \
 		browser_inspector_treePanel_result.html \
+		browser_inspector_registertools.js \
 		browser_inspector_bug_665880.js \
 		$(NULL)
 
diff --git a/browser/base/content/test/inspector/browser_inspector_registertools.js b/browser/base/content/test/inspector/browser_inspector_registertools.js
new file mode 100644
index 000000000000..04e9364df856
--- /dev/null
+++ b/browser/base/content/test/inspector/browser_inspector_registertools.js
@@ -0,0 +1,275 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Inspector Highlighter Tests.
+ *
+ * The Initial Developer of the Original Code is
+ * The Mozilla Foundation.
+ * Portions created by the Initial Developer are Copyright (C) 2011
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *   Michael Ratcliffe <mratcliffe@mozilla.com>
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+let doc;
+let h1;
+let tool1;
+let tool2;
+let tool3;
+
+function createDocument()
+{
+  let div = doc.createElement("div");
+  let h1 = doc.createElement("h1");
+  let p1 = doc.createElement("p");
+  let p2 = doc.createElement("p");
+  let div2 = doc.createElement("div");
+  let p3 = doc.createElement("p");
+  doc.title = "Inspector Tree Selection Test";
+  h1.textContent = "Inspector Tree Selection Test";
+  p1.textContent = "This is some example text";
+  p2.textContent = "Lorem ipsum dolor sit amet, consectetur adipisicing " +
+    "elit, sed do eiusmod tempor incididunt ut labore et dolore magna " +
+    "aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco " +
+    "laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure " +
+    "dolor in reprehenderit in voluptate velit esse cillum dolore eu " +
+    "fugiat nulla pariatur. Excepteur sint occaecat cupidatat non " +
+    "proident, sunt in culpa qui officia deserunt mollit anim id est laborum.";
+  p3.textContent = "Lorem ipsum dolor sit amet, consectetur adipisicing " +
+    "elit, sed do eiusmod tempor incididunt ut labore et dolore magna " +
+    "aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco " +
+    "laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure " +
+    "dolor in reprehenderit in voluptate velit esse cillum dolore eu " +
+    "fugiat nulla pariatur. Excepteur sint occaecat cupidatat non " +
+    "proident, sunt in culpa qui officia deserunt mollit anim id est laborum.";
+  div.appendChild(h1);
+  div.appendChild(p1);
+  div.appendChild(p2);
+  div2.appendChild(p3);
+  doc.body.appendChild(div);
+  doc.body.appendChild(div2);
+  setupHighlighterTests();
+}
+
+function setupHighlighterTests()
+{
+  h1 = doc.querySelectorAll("h1")[0];
+  ok(h1, "we have the header node");
+  Services.obs.addObserver(inspectorOpen, "inspector-opened", false);
+  InspectorUI.toggleInspectorUI();
+}
+
+function inspectorOpen()
+{
+  info("we received the inspector-opened notification");
+  Services.obs.removeObserver(inspectorOpen, "inspector-opened", false);
+  Services.obs.addObserver(startToolTests, "inspector-highlighting", false);
+  let rect = h1.getBoundingClientRect();
+  executeSoon(function() {
+    EventUtils.synthesizeMouse(InspectorUI.highlighter.iframeDoc.documentElement,
+             rect.left + 2, rect.top + 2, {type: "mousemove"},
+             InspectorUI.highlighter.iframe.contentWindow);
+  });
+}
+
+function startToolTests(evt)
+{
+  info("we received the inspector-highlighting notification");
+  Services.obs.removeObserver(startToolTests, "inspector-highlighting", false);
+  InspectorUI.stopInspecting();
+
+  info("Getting InspectorUI.tools");
+  let tools = InspectorUI.tools;
+  tool1 = InspectorUI.tools["tool_1"];
+  tool2 = InspectorUI.tools["tool_2"];
+  tool3 = InspectorUI.tools["tool_3"];
+
+  info("Checking panel states 1");
+  ok(tool1.context.panelIsClosed, "Panel 1 is closed");
+  ok(tool2.context.panelIsClosed, "Panel 2 is closed");
+  ok(tool3.context.panelIsClosed, "Panel 3 is closed");
+
+  info("Calling show method for all tools");
+  tool1.onShow.apply(tool1.context, [h1]);
+  tool2.onShow.apply(tool2.context, [h1]);
+  tool3.onShow.apply(tool3.context, [h1]);
+
+  info("Checking panel states 2");
+  ok(tool1.context.panelIsOpen, "Panel 1 is open");
+  ok(tool2.context.panelIsOpen, "Panel 2 is open");
+  ok(tool3.context.panelIsOpen, "Panel 3 is open");
+
+  info("Calling selectNode method for all tools");
+  tool1.onSelect.apply(tool1.context, [h1]);
+  tool2.onSelect.apply(tool2.context, [h1]);
+  tool3.onSelect.apply(tool3.context, [h1]);
+
+  info("Calling hide method for all tools");
+  tool1.onHide.apply(tool1.context, [h1]);
+  tool2.onHide.apply(tool2.context, [h1]);
+  tool3.onHide.apply(tool3.context, [h1]);
+
+  info("Checking panel states 3");
+  ok(tool1.context.panelIsClosed, "Panel 1 is closed");
+  ok(tool2.context.panelIsClosed, "Panel 2 is closed");
+  ok(tool3.context.panelIsClosed, "Panel 3 is closed");
+
+  info("Showing tools 1 & 3");
+  tool1.onShow.apply(tool1.context, [h1]);
+  tool3.onShow.apply(tool3.context, [h1]);
+
+  info("Checking panel states 4");
+  ok(tool1.context.panelIsOpen, "Panel 1 is open");
+  ok(tool2.context.panelIsClosed, "Panel 2 is closed");
+  ok(tool3.context.panelIsOpen, "Panel 3 is open");
+
+  gBrowser.selectedTab = gBrowser.addTab();
+  gBrowser.selectedBrowser.addEventListener("load", function() {
+    gBrowser.selectedBrowser.removeEventListener("load", arguments.callee, true);
+    waitForFocus(testSecondTab, content);
+  }, true);
+  
+  content.location = "data:text/html,registertool new tab test for inspector";
+}
+
+function testSecondTab()
+{
+  info("Opened second tab");
+  info("Checking panel states 5");
+  ok(tool1.context.panelIsClosed, "Panel 1 is closed");
+  ok(tool2.context.panelIsClosed, "Panel 2 is closed");
+  ok(tool3.context.panelIsClosed, "Panel 3 is closed");
+
+  info("Closing current tab");
+  gBrowser.removeCurrentTab();
+
+  info("Checking panel states 6");
+  ok(tool1.context.panelIsOpen, "Panel 1 is open");
+  ok(tool2.context.panelIsClosed, "Panel 2 is closed");
+  ok(tool3.context.panelIsOpen, "Panel 3 is open");
+
+  executeSoon(finishUp);
+}
+
+function finishUp() {
+  InspectorUI.closeInspectorUI(true);
+  gBrowser.removeCurrentTab();
+  finish();
+}
+
+function test()
+{
+  waitForExplicitFinish();
+  gBrowser.selectedTab = gBrowser.addTab();
+  gBrowser.selectedBrowser.addEventListener("load", function() {
+    gBrowser.selectedBrowser.removeEventListener("load", arguments.callee, true);
+    doc = content.document;
+    waitForFocus(registerTools, content);
+  }, true);
+  
+  content.location = "data:text/html,registertool tests for inspector";
+}
+
+function registerTools()
+{
+  registerTool(new testTool("tool_1", "Tool 1", "Tool 1 tooltip", "I"));
+  registerTool(new testTool("tool_2", "Tool 2", "Tool 2 tooltip", "J"));
+  registerTool(new testTool("tool_3", "Tool 3", "Tool 3 tooltip", "K"));
+  createDocument();
+}
+
+function registerTool(aTool)
+{
+  InspectorUI.registerTool({
+    id: aTool.id,
+    label: aTool.label,
+    tooltiptext: aTool.tooltip,
+    accesskey: aTool.accesskey,
+    context: aTool,
+    onSelect: aTool.selectNode,
+    onShow: aTool.show,
+    onHide: aTool.hide,
+    panel: aTool.panel
+  });
+}
+
+// Tool Object
+function testTool(aToolId, aLabel, aTooltip, aAccesskey)
+{
+  this.id = aToolId;
+  this.label = aLabel;
+  this.tooltip = aTooltip;
+  this.accesskey = aAccesskey
+  this.panel = this.createPanel();
+}
+
+testTool.prototype = {
+  get panelIsOpen()
+  {
+    return this.panel.state == "open" || this.panel.state == "showing";
+  },
+
+  get panelIsClosed()
+  {
+    return this.panel.state == "closed" || this.panel.state == "hiding";
+  },
+
+  selectNode: function BIR_selectNode(aNode) {
+    ok(InspectorUI.selection, "Currently selected node was passed: " + this.id);
+  },
+
+  show: function BIR_show(aNode) {
+    this.panel.openPopup(gBrowser.selectedBrowser,
+                         "end_before", 0, 20, false, false);
+    ok(InspectorUI.selection, "Currently selected node was passed: " + this.id);
+  },
+
+  hide: function BIR_hide() {
+    info(this.id + " hide");
+    this.panel.hidePopup();
+  },
+
+  createPanel: function BIR_createPanel() {
+    let popupSet = document.getElementById("mainPopupSet");
+    let ns = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
+    let panel = this.panel = document.createElementNS(ns, "panel");
+    panel.setAttribute("orient", "vertical");
+    panel.setAttribute("noautofocus", "true");
+    panel.setAttribute("noautohide", "true");
+    panel.setAttribute("titlebar", "normal");
+    panel.setAttribute("close", "true");
+    panel.setAttribute("label", "Panel for " + this.id);
+    panel.setAttribute("width", 200);
+    panel.setAttribute("height", 400);
+    popupSet.appendChild(panel);
+
+    ok(panel.parentNode == popupSet, "Panel created and appended successfully");
+    return panel;
+  },
+};