Your watchers want to know whether you are watching them, to twist a phrase.
"Microsoft believes the key differentiator between Xbox as a TV platform and the sea of failed competitors will be its voice and motion search tool. Utilizing the Kinect attachment, users will be able to be identified by number and state of activity, providing valuable feedback to the content providers and their customers, the advertisers." Fixed that for you.
Bonus if they build profiles of individuals and estimate ages by correlating with easily available databases and public records. Extra bonus if Microsoft listens to all other programming being played in the room and identifies it audibly.