javascript unload event in safari mobile?

I'm working on a webapp for 开发者_如何学编程iPad with jQtouch and jQuery. The webapp is used in a store and viewed through AVD browse which send me email alerts when the device is shook or disconnected from power. However, I also want to know when the webapp has been closed. I tried to use $(window).bind('unload', function(){}); but it doesn't work neither in Safari Mobile nor AVD browse. How can I get it to work?

I have an answer. It's not what we were hoping for.

The technical definition of unload from http://www.w3.org/TR/DOM-Level-2-Events/events.html is:

The unload event occurs when the DOM implementation removes a document from a window or frame. This event is valid for BODY and FRAMESET elements.

I also got a reply from some in the know at Apple: "Unfortunately, I haven't been able to find an event that fires when the Home button is clicked! I think the most appropriate event for this might be the pagehide event. This event actually does fire in Safari on iOS when you switch to the "tabs" view to open a new page, but not when you click the home screen icon :-("