There's been several attempts at noninvasive biosensing using techniques like Raman spectroscopy, but it's a lot harder to make it reliable than people estimate

There's been several attempts at noninvasive biosensing using techniques like Raman spectroscopy, but it's a lot harder to make it reliable than people estimate. Apple recently shelved its program for doing glucose sensing from the watch, which I remember Tim Cook had remarked would be straightforward. On top of that, the places where DARPA wants these sensors to be deployed (MCIs, trauma victims) make for very difficult sensing environments (due to blood loss, shock, hyperglycemia etc)