Creating a new GestureRecognizer

Looking at the Xamarin.Forms Api tha you provide, there is only TapGestureRecognizer. I was thinking of implementing more GestureRecognizers. However, in the interface that you guy provide is

using System;
using System.ComponentModel;

namespace Xamarin.Forms
{
public interface IGestureRecognizer : INotifyPropertyChanged
{
}
}

Any more information that I missing on how to implement a new GestureRecognizer.

Note: I will post it to github once ready.