Sorry for having the coffee break one year .. I am back. Coffee was good.
Xamarin cross-platform tools is good, but I don't understand why we need to develop the entire mobile app in Xamarin. Whatever is not UI code and thus does not need to be using native framework (Cocoa, Android ...) should be written in Xamarin code (C#, F#...you pick). This way the Xamarin is faster than the native framework in most cases.
By now, mobile applications are developed as one piece,,,,It is not a very good idea, because the maintainability cost is going thru roof months later.
All communication can be done via pipes or sockets.
I am experimenting with this approach as time allows and hopefully soon I will be able to show the "framework" I am putting together.