Some enterprising dudes out there have figured out that the Nintendo Wii’s “Sensor Bar” doesn’t actually “sense” anything. In fact, the sensor bar appears to simply be a set of IR transmitters that provide the Wii-mote with a sense of direction. They recorded their findings and posted this video showing how it works.
The video seems to prove that all the hard work is done by the Wii-mote itself, and that you can even run the system without the sensor bar in place as long as you have another source of IR for the remote to triangulate off of (in this case a pair of regular old IR remote control.) Be sure to check out the end of the video, where the camcorder actually picked up the IR output from the sensor bar.