Last week, at the Xamarin Evolve conference, Xamarin announced support for the F# language as part of the Xamarin tools for iOS and Android app programming. Microsoft were Platinum sponsors of Xamarin Evolve.
Videos from Evolve will be available soon (link). In the meantime, you can watch Miguel de Icaza, one of the founders of Xamarin, discuss the F# support they have added (the F# part starts at 21min 55s) in this Channel 9 video
The announcement from Xamarin means you can now create iOS and Android applications using 100% F# code, or alternatively use the C#-F# pattern where front-end logic is in C# and some or all application components are in F#. As an example, here is a PacMan game for iOS written entirely in F#. In this case nearly all the game logic can be shared across iOS, Android, Windows 8 (in portable libraries), Windows 8 Phone and WPF.
Somewhat surprisingly, the announcement from Xamarin means F# now has one of the broadest cross-platform development stories amongst all functional-first languages (e.g. it is difficult to use Scala on iOS at the moment, according to this link). In addition, we have the wonderful editions of Visual F# from Microsoft.
The F# Software Foundation provide some instructions on how to get going with the Xamarin tools at http://fsharp.org/use/android and http://fsharp.org/use/ios.
Thanks to Charles at Microsoft Channel 9 for doing the interview with Miguel. And well done to Xamarin and the F# open source community for making this happen.