I just finished playing with the new USB Wii Sensor Bar that I made.
It’s not very pretty, but it works. I just plug it into my USB port, and the infrared LED’s light up. From there, the Wii remote (connected to my computer over Bluetooth), figures out where to put the mouse using a GlovePIE script.
I made it from an old USB cable, four IR LED’s, two wires, a bit of perf board, and a wad of sticky tack.
If you want to make your own sensor bar, there are some great instructions for a much better looking finished product that I followed to wire this up.