If you are looking for behaviors in WinRT with MvvmCross, you can now use the Windows.UI.Interactivity nuget package for it (https://nuget.org/packages/Windows.UI.Interactivity).
When using it with MvvmCross, I made a copy with some small alterations to the existing MvxEventToCommand class (inherit from TriggerAction(FrameworkElement) instead of TriggerAction(DependencyObject)). Works like a charm.
This is excellent news - it's going to save me from so much ugly code behind work :)
Definitely awesome - and it bags GitteTitter a WinRT-flavoured MvvmCross Badge of Awesomeness - thanks!
(Sorry - I couldn't find any slick chips+mayonnaise clipart to make the look more Belgian!)