I have a MonoTouch or WindowsPhone 7 application, can I just rebuild it with Mono for Android and target Android?
Both Mono for Android and MonoTouch bring the core of .NET to the iPhone and Android platforms, but we do not offer a UI cross-platform solution. Each operating system offers slightly different services for building user interfaces, interacting with the phone, the address book, the built-in GPS and audio systems. Our recommendation for users that want to target all three mobile platforms is for developers to separate the business logic of their application from the user interface and hardware interface layer. This means that both the user interface layer and any hardware integration components will have to be written once for each platform. Your business logic can consist of anything that uses the core APIs in: mscorlib, System, System.Xml, System.Core, System, System.Data, System.Json, System.Runtime.Serialization, System.ServiceModel, System.Web.Services and System.Xml.Linq. In addition, OpenGL code between the iPhone and Android can be shared as we support the OpenTK API, an object-