Microsoft Research shows a Dance Dance Revolution style user interface at the Microsoft TechFest.

With the Microsoft Computer Foot Pad you can 'walk' through your email and photo library.
This is just one out of 150 concepts presented at the Microsoft TechFest - a kind of internal idea fair.
To include feet in interacting with a computer is interesting. Lots of other devices have a foot interface, e.g. Cars, Sewing machines, etc.
More photos and details in this AP story on Yahoo!. See also the Microsoft TechFest press-release.