Even if you couldn't imagine this, as you say, the Playstation Eye camera has a rather capable microphone array built in, which is capable enough for what you described. Some games, take Singstar for example, have had voice commands for some time now (I think, two years or something), it's just that Sony doesn't value that feature highly enough to make them put it into the firmware, and use it system wide.
I don't long for it, either, by the way. I mean, who wants to have a feature that enables their spouse to shout: "xbox, force shutdown!" across the room whenever they are disgruntled about something? Or all the inadvertent voice commands the system tries to execute whenever you are having a ball with some friends? On a more serious note: contrary to Wiimote 2.0 (or whatever it's called), and Playstation Move, Kinect doesn't seem to live up to its specifications, or rather, people's expectations. Lag is still massive, the system can't track more than two players at the same time (expect disruptions whenever party people crowd up around the players, and while you're at it: strip the cameras' field of vision of any distractions like sofas, bookshelves, rotating fans, and the like!), it's by far the most expensive motion control system of all the consoles because you'll have to buy the whole set and can't scale it up over time, like with Move.