Custom Drawing

Haven't posted a topic myself lately, but I'm running into some questions.

Ive been doing several projects now, and i want to do more then the standard stuff.
For example let's say. if the user draws an Circle on the screen (without any lines following or nothing). it should give me an OK, or something similair.
Just, how do u make the custom gestures.
Just interested in some pointers to websites who explain or something.

Thanks for the read,

Gz, Noxx.

 

I'm sorry for my hasty topic creating.
I found a tutorial here -->

http://mobileorchard.com/iphone-circle-gesture-detection/

Hope anyone needs it too