add_debug_extension(
	'actions', #Mode
	__('Actions', 'debug-this'), #Label
	__('$wp_actions contains all active registered actions', 'debug-this'), #Description
	'foo_callback', #Callback - accepts object methods as well
	'Filters And Actions' #Admin Bar Group
);
function foo_callback($buffer){
	#Do something
	#$debug contains the rendered page/post HTML
	return $debug;
}