How do I create an application that works on both the Windows 7 Phone and IPhone?

Question

It is clear that Mono Touch is part of the solution as it allows C# code to run on the IPhone, however Mono Touch wraps the IPhone API so does not provide a common API.

Answer 1

Mobile platforms are far from being versatile and act in singularity, Chances are high they'll end up with holistic war much like browsers of today. If I were you, then I'd straight away take a decision to write two separate apps. Even if you get to write some apps using Mono, tomorrow you'll surely have issues with features compatibility commonly or distinctively supported on both phone platforms.

Bottom line is if you wish to leverage from the platform stick to the native platform SDK and tools.