Yeah, i've been having a look at it...bugger me! it's the most confusing thing i've ever experienced.

processing.org/download/

My guess would be that hes taking in data from the webcam and figuring out tilt based on the image of himself. Maybe hes "cheating" and has a marker on his body, like a colored square or rectangle to capture. But maybe he does have a sensor built into that laptop, that would rule!

New Apple laptops have effectively motion sensors built-in, basically to protect the hard-drive. You can have more infos and source code here :)
v3ga.net/blog/2006/12/pomme-damour/