My ExtJS app runs on the iPhone. It takes about 10 minutes to load, though. And for some reason, Apple still has some big fear of right mouse buttons (there's no way to bring up context menus on the iPhone).
ExtJS does technically work on phone based browsers, though its a tad heavy for them to handle.
The bigger problem that you will have to address, is that an app developed for the desktop will not be usable on a phone without significant design changes. The same would be true if you were to put you app on a touchscreen kiosk for instance.
There might be an alternative architectural solution but it's not simple to implement and may be infeasible.