I really like the concept at 3 minutes by using the white page and a logo as a tracking pattern.
It's like a reverse movement captation (a computer vision gyroscope !).
SixthSense from Fluid Interfaces on Vimeo.
Found here http://vimeo.com/17567999
"'SixthSense' is a wearable gestural interface that augments the physical world around us with digital information and lets us use natural hand gestures to interact with that information. By using a camera and a tiny projector mounted in a pendant like wearable device, 'SixthSense' sees what you see and visually augments any surfaces or objects we are interacting with. It projects information onto surfaces, walls, and physical objects around us, and lets us interact with the projected information through natural hand gestures, arm movements, or our interaction with the object itself. 'SixthSense' attempts to free information from its confines by seamlessly integrating it with reality, and thus making the entire world your computer."