This morning I came across one of the most amazing games, it was linked to from a user on Pownce and its called Crayon Physics and involves moving a circle across the screen to the star on the other side. The website describes a version that is still in development but the original game can be downloaded. The games uses a physics engine to control drawn shapes, for example if you draw a circle it will fall down under gravity and interact with other objects. The game ideally needs to be placed on a tablet PC as the pen interface seems essential.
For example in the level above you can draw an oblong between the two towers and then knock the ball along, the video on the website describes it better.
I can't wait for the deluxe version, you can make a car!