Honestly, doing this backend work is pretty trivial. Aside from Windows Phone that is, where everything must be in managed code (doh). But iPhone / Android is t

Honestly, doing this backend work is pretty trivial. Aside from Windows Phone that is, where everything must be in managed code (doh). But iPhone / Android is trivial, like literally a couple of days for a moderately complex app with storage, threading, background downloading, and so on. Even input isn't too bad for simple gestures. The real work for non-game apps is converting all of your UI and device interactions to the new OS. Linux compatibility might let you avoid rewriting your code that opens files, bit it's not going to let you make a UI element pulse for a few seconds then drop off the screen.