Foveon sensors are a really neat idea that will never see a proper implementation in to a real world product as long as Sigma owns the patent to the technology and doesn't license it. Mike Johnson, who runs the excellent photography blog The Online Photographer, had a great article last year about foveon technology. He compared the Foevon sensor to Lincoln Walsh's speaker drivers, which are the only used in Ohm brand speakers. The article is a good read for photo nerds, audio snobs or those of us who happen to be both.