MVVM-light is a toolkit written in C# which helps to accelerate the creation and development of MVVM applications in WPF, Silverlight, Windows Store, Windows Phone and Xamarin.
Webpage: http://www.mvvmlight.net/
There is a cross-platform MVVM sample from the author of the library which can be found at https://github.com/lbugnion/sample-crossplatform-flowers