Steering Wheel UI Controller.

I am trying to create the same controller as the guys from Crywolf Studios made for the Invading Insanity game.

Video: http://www.youtube.com/watch?v=QVMn3NqtjMs

Would I be wasting my time if I tried to find the center of the disk position, the finter's touch position on the screen, and then get the angle from that which the disk needs to rotate?

What approach would you take? I love how the disk in the video is following the finger.