Update README

README.md

@@ -133,3 +133,11 @@ tc.channel.sender.send_time = 5
 # the background worker thread will poll the queue every 0.5 seconds for new items
 tc.channel.sender.send_interval = 0.5
 ```
+
+###Collecting unhandled exceptions###
+```ruby
+require 'application_insights'
+# setup unhandled exception handler
+ApplicationInsights::UnhandledException.collect('<YOUR INSTRUMENTATION KEY GOES HERE>')
+# raise an exception and this would be send to Application Insights Service
+raise Exception, 'Boom!'

lib/application_insights/unhandled_exception.rb

@@ -17,7 +17,8 @@ module ApplicationInsights
     #   raise Exception, 'Boom!'
     def self.collect(instrumentation_key)
       at_exit do
-        send(instrumentation_key)
+        # Avoid sending exception more than once if this method got invoked multiple times
+        send(instrumentation_key) if !@sender
       end
     end