The Kinect is a great example of using the most expressive form of interaction we have - our entire body. It's the right idea. The latest updates even do facial recognition (identify muscle movement). Too bad it doesn't scale to smaller devices/cramped objects. I wonder how small kinect-like tech has to get before it makes its way into smart phones, etc.

However, I think voice might be a more expressive medium there, even better than touch. Imagine being able to detect sarcasm, inflection, accent, etc!