[CretinDesAlpes]

For those interested in the pulse rate extraction, there is actually a branch of biomedical engineering/computer science called "remote photoplethysmography" (rPPG).

I worked on it a bit at some point, it does work pretty well assuming you don't move that much and the light isn't too bad. As you can imagine, it's more difficult to estimate on non-white faces, particularly very dark skin tones. All the algorithms (at least until 2016) differ in the way of combining the RGB signals into a pulse signal by making different assumptions.

If you are interested more, Philips in the Netherlands are particularly active in this research domain, one of the main application being non-contact pulse estimation in hospitals for example.