Basically, the Wii remote is a Bluetooth device. It has four IR cameras on it, and if you use a Bluetooth-capable notebook or PC, you can use the Wii remote as a tracking device for any IR source in the field of view of the Wii remote. If you attach a IR LED on top of a pen, the IR pen can be a "mouse" of sorts.
No Wii required. You'll need Johnny's program, found here.
Video can be seen here:
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