Last Saturday I had a chance to jump on a pretty cool mixed reality installation: Physical Virtuality, a hydraulic-equipped platform connected to Second Life from Museumnacht in Amsterdam, and "extended" as a virtual platform into SL's Popcha island. (Home to the Brooklyn is Watching mixed reality project.)
So basically, this is a seesaw with one half in the metaverse, the other half in reality. A scripting system estimates the weight of avatars standing on the SL side (if they existed, that is), and shifts the Museumnacht platform accordingly. At the same time, people in Amsterdam can move around on the real world side of the platform, which causes a proportionate reaction on the SL side. A live video link displays the action from Amsterdam into SL, and vice versa.
It's a fun idea, though when I visited, people were far outnumbered by avatars, so there wasn't much interactivity coming from the real world. (Then again, maybe that's because the SL side was weighed down by a purple-haired babe bench pressing several hundred pounds.) Also, the hydraulic shifting process wasn't moving fast enough to really acheive a fully believable RL-to-SL seesaw action. Still, I'd love to see more projects like this. So far, the most impressive one I've seen involved a giant Second Life robot hooked up to an accelerometer control in Japan.
Thanks to Frans Charming for the tip; the longtime Dutch Resident helped control the real life side from Amsterdam.