This is very, very cool. Umoove Experience is a free, universal iOS game that lets you fly through a 3D environment and control your motions by moving your head and eyes. The game is more a technology demonstration than a full-blown game, but it's sure to give game developers some good ideas.
When you start the game, it activates the front-facing camera. You are asked to move your head in four directions, and the app records your profile and movements.
The game begins as you fly above a 3D-rendered village, and you change your course trying to grab purple magic potions, which extend your lifetime and let you explore the village environment. Once you get used to it, which doesn't take long, the game really is a pleasure to use. While flying around could get old after awhile, the fact that you are interacting with your hardware and the 3D game with slight movements feels quite liberating.