Here is a demo of the Kinect and what it can do (about 12 min). Crazy that the camera is so sensitive it can tell you your heart rate.
A camera doesn't have to be sensitive to detect heart rate. There are some algorithms from MIT that exaggerate motion and changes in color.
http://www.youtube.com/watch?v=3rWycBEHn3s
Here's a gif to give you the idea if you don't want to watch the video.
at 2:22 in the video, they show Christian Bale's pulse from a Batman clip and they talk about baby monitor video, so I don't know how high a resolution they need, but there's nothing special about the video sensitivity in terms of color and light.