I was going to recommend pulse estimation, but then I recognized that I had already recommended that to you in another post This is because, I believe, the pulse is calculated from the color of the blood under the skin, which is similar to how a face is flushed by temperature.
Yes, the hear rate use the IR to get the blood flow, but I don't know how it does :/
Intel staffer Colleen Culbertson had this to say about pulse estimation: "Pulse estimation tracks subtle change in face skin color over time and estimates the person's pulse rate. The algorithmic range shows as 30-60cm on the F200."
Some university people wrote an extremely detailed paper on the feature.
And another version of that research.
Thanks, but I can't find the way that they extract the temperature, just the variations of it...
if anyone can help it would be great!