Bind events directly to the container, typically a div element.  Use jQuery Mobile's virtual events, or bind standard JavaScript events, like change, focus, blur, etc.:
$( ".selector" ).bind( "collapse", function(event, ui) {
  ...
});
The collapsible plugin has the following custom events:
create triggered when a collapsible is created
$( ".selector" ).collapsible({
   create: function(event, ui) { ... }
});
			collapse triggered when a collapsible is collapsed
$( ".selector" ).collapsible({
   collapse: function(event, ui) { ... }
});
			expand triggered when a collapsible is expanded
$( ".selector" ).collapsible({
   expand: function(event, ui) { ... }
});