The ship in Omegapixel is controlled via a virtual joystick. The touch screen is not well suited to joystick like input and it is hard to get right. Omegapixel was built using cocos2d so we had the option to use SneakyInput, but we opted to roll our own code.
We've received a number of questions about the input code that we used, so I've decided to publish psuedocode of the implementation:
If you get a chance, give Omegapixel a try and let us know what you think: Omegapixel on the App Store.