Xamarin now also supports writing iOS and Android apps in F#; it's only a "preview" at the moment, but some of the Mono developers have been getting more involved in the F# open-source community and Xamarin recently hired a well-known, very skilled F# contractor to help improve their support for the language.

Xamarin's website has a bit more information: http://docs.xamarin.com/guides/cross-platform/fsharp/fsharp_...