If you want to stay in the "Unity state of mind" and keep your code platform independent (even if just so you can easily test on your desktop), I found the easiest way to handle gestures is using one of the gesture plugins.

I can recommend two:

1. [TouchKit by Prime31][1] - free and open source
2. [Input.Touches][2] - available in the asset store, not free.


  [1]: https://github.com/prime31/TouchKit
  [2]: http://forum.unity3d.com/threads/133991-Input-Touches-Simple-Gesture-Solution