Remember that crazy, bulbous PS3 motion controller spotted in a Sony patent app? Well a newly uncovered Sony application is slightly less Requiem for a Dream and slightly more Captain Planet.
Diagramed to work with the PS2 (but probably just as applicable to the PS3), Sony recounts variably-colored LEDs that fit on your fingers. A regular camera (like the EyeToy) tracks these LEDs—a task that's easy even in dark environments.
My gut tells me that this patent is a dated, defensive maneuver—the once-solution to the fundamental flaw with Nike's Kinetic for PS2. The exercise game was fantastic, but it just couldn't track user movement all that well in any sub-optimal lighting conditions. Then again, newer PS3 games (like Trials of Topoq) are based upon the same motion-tracking premise and they, too, are hindered by low light.