windowMessenger is a jQuery UI Widget that when installed on two windows allows the two windows to communicate back and forth with each other (such as a window communicating with a child iFrame or child to parent). Communication between windows is accomplished by using the browser window's postMessage() method to send messages between windows. This allows for both same domain and cross domain communication.
windowMessenger also has the ability to execute methods that exist on the other window or send functions across to be executed on the other window. This is a very powerful ability, but make sure you are aware of the security risks involved with cross window communication. This is covered further in the Wiki.
To learn how to integrate windowMessenger into your project, please read the documentation available in the Wiki.