Tutorials for Writing Common Code for use on Windows, OS X, iOS, and potentially Android

I'm looking at writing an application that I would like to use on Windows, OSX, and iOS (maybe pushing into Android if other people want to use it). I want to duplicate as little work as possible and I'm having a hard time finding information on the best way to do this.

From what I've found so far I can't use a framework like QT because iOS doesn't support QT so it looks like I'm stuck recreating the interface for each target. I'm looking at writing the business logic in C++ because it seems to be supported by the native tools (Visual Studio and xCode).

Has anyone had experience with a setup like this and if so can you point me towards a good reference 开发者_JAVA百科for this kind of development?

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Really there it not a lot of choice right now. Qt is certainly coming to iOS and WP7 so C++ is a good solid evolving platform.

However there is also the mono project which offers C# across platforms.

http://xamarin.com/monoforandroid

From my understanding, you write in c# and it compiles to the platforms preferred language.