How to enrich basic WPF gestures?

I'm currently working on a project with a multi-touch screen on Windows 8 Pro / Visual Studio 2013 / C# / WPF / .NET 4.5.

I'd like to know how you would add your own gestures to the basic ones like ManipulationStarting, ManipulationDelta, ManipulationInertiaStarting ?
FYI, I've already read the article http://msdn.microsoft.com/en-us/library/ee649090%28v=vs.110%29.aspx

For example, how would you detect a hold gesture or a double tap ?