That is key. I don't see how. At first I thought maybe a sweat related method? Perhaps some odd electronic field trick no on has tried? Unlike heart rate I doubt a camera and bright light would suffice.

I do know I would buy them for my parents immediately once they are shown to work. Would not even pause. Blood sugar is spooky and you are toast if it goes low and no one is around to help

anecdotal section : My mother has been taking insulin since the 80s, she uses a pump currently. The real danger in blood sugar is when levels get low. She has caught her self in the low 40s but if it had happened at night she would be in real trouble. You just simply go to sleep and never wake from it. High numbers while dangerous are sustainable and your conscious throughout.

She has had a few episodes where it went out of control (600+) that took a hospital visit days to get under control with a drip. Same routine, you go in and tell them your level. They don't believe you. They test three times then freak out. You are in heart ward and even then they cannot get it back and turn from blaming your diet to going "We don't know". The point is, even highly regulated/monitored things happen and doctors don't know all the whys.