Don't forget that the Kinect will be able to sense ambient noise to alert or distract zombies in Dead Rising 3. Horror games could use the kinect to sense your heart rate, degree of pupil dilation or general posture to determine the best time to send that monster your way. If you're swimming underwater in a game, the kinect could sense how long you can hold you breath and if you start breathing while still submerged reduce your health meter accordingly (this is probably best reserved for very hard difficulty settings).

What I'm trying to say is, you don't have to be shouting at your TV or waving your arms around like an orchestral conductor for the Kinect to provide a meaningful addition to your immersion in the gaming experience.

What other passive features can you think of?