Few extensions example can be found here. I suggest to analyze few extensions there and you will get an idea how all works.
If you want to activate extension you have to edit
and change the following part to
'extensions' => array ( 0 => 'customstatus' )
In this exmaple we are activating customstatus extension. Make sure you disable cache while developing.
How to attatch event listeners to extension? Just take a look at this file
In this class you can define to what events your extension should listen.
What events does Live Helper Chat dispatches? List of events
Here is example to what events Automated hosting extension is listening