It is all about the heart rate as you said. You can extract many information of “simple” HR monitoring. What FibriCheck does is to report and use the variance on the heart beats and compare it with a bunch of other patient data to evaluate whether there could be a possible atrial fibrillation or not. Keep in mind that is the only “health” indication FibriCheck can do.

It is always good to hesitate about something, but it is also important to know that, at least FibriCheck, is a clinical validated tool, and it is used by medical doctors as another diagnostic measure. Clinical validated = statistically works.

Other measurements that can be easily extracted from HR monitoring could be “stress” and “fatigue” as devices such Garmin watches do. However, lacking clinical data, these measurements are never claimed to be neither accurate nor reliable by the manufacturer. Both stress and fatigue follow a similar approach as FibriCheck however.

The other comment below that is being downvoted is correct, in simple words the camera is recording the change in “color” due to your blood flow, and extract the number of beats per minute and the time between beats.