Sony Computer Entertainment America filed a patent a couple months back, for a system using coffee mugs to play a video game. Now they've filed one to make your laughter into a controller.
I direct you to figure 17: "Ha Ha Ha." This is part of the metadata set going into the PS3, through a microphone and the PlayStation Eye camera. The patent application says it would identify body gestures, facial expressions and the like to deduce the emotion of the players. It's apparently got high-five recognition heuristics, too.
Laughter and boo-yah aren't the only states of emotion it'll be able to recognize. It's also attuned to sadness, anger, joy, interest and yes, boredom. That one can be detected by the number of hours your PS3 sits deactivated.
Also, note how the diagram filed goes out of its way to show the TV's a Sony Bravia.
SCEA Experimenting With "Laugh Detecting", Emotional Tracking Software [Siliconera via Joystiq]