A projected user interface for portable devices

Pattie Maes & Pranav Mistry: Unveiling the “Sixth Sense,” game-changing wearable tech
A nice demo of a device that uses a projector and image recognition to project its user interface onto external objects. This is an interesting contribution to exploring the extremes of immersive user interface on one hand and external user interfaces on the other hand.
Update: More user interface ideas:
David Merrill: Siftables, the toy blocks that think