Sorry, There is and we do. http://kivy.org/ It may not use native widgets, but that's a good choice to my mind. It's entirely consistent across platforms and in many ways, that's a lot easier to handle that catering of OS specific behaviour.

http://kivy.org/

It's utterly trivial with Kivy (http://kivy/org). You have virtually no OS differences unless you want to make use of OS specific functionality. Thankfully, Kivy provies Python wrappers for native iOS and Android calls via Objective C and Java wrappers. It really works well and it's truly open: MIT licensed...;-)

Why not use Python and run on iOS/Android/Windows/MacOSX/Windows with one codebase? http://kivy.org/