Since Nintendo pushed the envelope, hardware manufacturers seem intent on making new controller types. Now that each of the big gaming companies have at least dabbled with motion controls, biometric feedback seems to be the next big thing. Sony is looking into biometric controllers to measure factors like sweat and heart rate. Not to be outdone, Microsoft is apparently considering a pressure-sensitive controller. The company has registered a US Patent (8,172,675) for a controller with a "pressure-sensitive exterior surface." The patent suggests that device memory could store the output signatures to identify users simply by how they grip the controller. And confirming that these plans relate to gaming, the patent also mentions the device as "a game controller that interacts with a game console service."
The patent makes repeated mention of the controller being used for identification, but doesn't go much deeper than that. Microsoft could potentially find gaming utilities, but doesn't seem to be going in that direction with the initial patent application. As always, a patent doesn't mean a product will ever come to market.