Maintaining product for Android + iPhone

This is a question to all of you out there who develop for both Android and iPhone. How do you maintain support for the two platforms? Specifically, do you

• maintain the two products totally separate from each other?
• create "native" GUIs in Java/ObjC and a "core" library in C/C++?
• write both versions in the same language (e.g. Java) and a third-party tool to generate code for each platform?
• write everything in the same c开发者_如何学编程ode base and use an even more fancy tool to generate native bindings for each platform?

I do create "native" UIs in Java/ObjC and core library is usually in C/C++. That's when the application I am maintaining requires a complex core library.

When the application is simple enough, I just maintain two code bases: Java/ObjC-CocoaTouch.

As far as I know, there are no fancy tools to generate binding for each platform. Maybe Monotouch will officially support Android at some point and you will be able to do everything in C#: Android, iPhone and Windows Phone 7!