カスタムな当たり判定を設定するには

Create-Custom-button-like-human-Hand.md

##Create Custom button like human Hand

I think at first you have to make polygon which fit to your image. And then you can use touchesBegan:withEvent: to get the coordinate of touch point and judge whether the point is inside of polygon or not.

Here is similar question like yours.

http://stackoverflow.com/questions/8450967/how-to-get-particular-touch-area

I think this is a little difficult work, so maybe you would better use cocos2d library which have collision judgement function.

http://box2d.org/forum/viewtopic.php?f=9&t=7487

But also I think iOS is well constructed for handling touch, so this is beneficial effort for you.