IPad for disabled person? control without touch

A friend of mine is disabled and not able to move anything but his head. I wanted to hack him some kind of computer system to give him access to ebooks and the internet. But I'm not quite sure how to do it, one option I'm seriously thinking about is an iPad. It's the only touch GUI you could control with one click only. Problem are input devices, at the moment I'm not sure how to control an ipad with dead or mouth movements only. Maybe eye tracking? Any ideas? I'm grateful for any suggestions.