"Rockley Photonics says that its system uses infrared spectrophotometers to detect and monitor a wider range of health issue than the green LED systems in most wrist devices."
I also remember paging through this fascinating investor presentation document from Rockley:
Looking at Rockley stuff in particular makes me hopeful this could be solved, if it's solvable with spectrophotometry at all. I'd even be OK with something larger, perhaps ankle-worn, as long as I don't have to puncture my skin at all.
