If the face of a "patient" was tied to his bed, and light wasn't changing, and there was no movement around (i.e. in ideal conditions), then yeah. But in the r

If the face of a "patient" was tied to his bed, and light wasn't changing, and there was no movement around (i.e. in ideal conditions), then yeah. But in the real world scenarios you want to take a look at more than one pixel, and use the rest of the picture for noise reduction & calibration. That is for heartbeat. But yes, with better spectral resolution you might get some other cool data.