Really cool application, I wanted to do something similar leveraging another app we built.

Usually when a client ask for such a rich mockup we build it in html and then we point an app that is a simple webview module. We use iScroll for the fix positioning of tabbar and nav bar and jtouch for the sliding windows.

Do you have any links to iScroll and jtouch? I'm searching but am not finding them.

http://www.jqtouch.com/ and http://cubiq.org/scrolling-div-for-mobile-webkit-turns-3 perhaps?

Someone should write an iPhone emulator iPhone app.

Emulators are not allowed, remember?