Comment by therealmarv

When I wanted to code a foundation of reusable code for different devices I would either do it like Dropbox and use C++ as the most common layer http://oleb.net/blog/2014/05/how-dropbox-uses-cplusplus-cros... or use Javascript (which I can also use for web pages) for the program logic like described here http://www.skyscanner.net/blogs/developing-mobile-cross-plat...

Also interesting http://kivy.org allows you to use Python for iOS, Android, OS X and Windows.

I would not bet on Swift and cross compiling it today... too bleeding edge. But interesting project... hope it matures. Good luck!