Sony has been patenting a series of concepts along these lines. Earlier this year the patented the ability to sense motion via a camera/PS3 system( http://www.siliconera.com/2009/08/14/scea-experimenting-with-laugh-detecting-emotional-tracking-software/). In product design you need to prove the concept(manufacture at any cost), prove the ability to manufacture(at a price point the consumer can afford), and approve the demand(provide something the consumer perceives as useful). This tech may be at the proof of concept stage for future consoles, but it is unlikely that Sony is considering it for this generation. In many ways they may be watching Natal's performance in the space to determine if there is any reason to move forward.
Thanks for the input, Jeff.
