I have this practice project that allows the user to draw on the screen as they touch with their fingers. Very simple App I did as exercise way back. My little cousin took the l
I've had pretty good luck with a properly trained $1 recognizer (http://depts.washington.edu/aimgroup/proj/dollar/). I used it for circles, lines, triangles and squares.
It was a long ago, before UIGestureRecognizer, but I think it should be easy-ish to create proper UIGestureRecognizer subclasses.