You guys have to see this video of the PICO computer interface in action. Very, very cool stuff!

PICO is a tabletop interaction surface that can track and move small objects on top of it. It has been used for complex spatial layout problems such as cellular telephone tower layout. The interface provides ample opportunities for improvisation by allowing the user to employ a rich variety of everyday physical objects as interface elements. The physical form of many everyday mechanical systems helps users quickly discover how these systems work and how to use them. One example is the record turntable. Because the mechanism through which this device functions is exposed to the user, some users have developed interaction techniques that the inventors of the device likely had never imagined, such as "scratching" the record as a part of musical performance. In a similar spirit, we have developed a system called Pico (Physical Intervention in Computational Optimization) that simultaneously represents and controls the high level structure of a software process with a mechanical process. The user can leverage his or her mechanical intuition about the way physical objects respond to forces and interact with each other to understand how common objects, such as a rubber band or coffee cup, might be used to constrain the underlying software process. Objects on the Pico table are moved not only under software control using electromagnets but also by users standing around the table. The combination of these interactions, all governed by the friction and mass of the objects themselves directly affects the result of the task being performed. Additional information is graphically projected onto the table from above. To date we have built Pico applications for factory floor plan layout, CNC toolpath optimization, and cellular telephone tower layout.