[jniedrauer]

My Garmin has a thermometer, but its purpose is to track barometric pressure. It doesn't accurately reflect my body temperature. When I go running below freezing, it usually drops down to around ~2* C. It may accurately reflect the temperature of the skin on my wrist but it's useless for telling me that I have a fever.

[exabrial]

I think the accurate readings would come when you're at rest sleeping, not hiking in freezing cold. The motion sense capability of these wearables would take that into affect. Garmin has a O2 sensor that comes on only when you sleep, it would make sense this would maybe do the same.

It looks like this tech does exist in rudimentary form, for females, and it's specifically tied for fertility tracking.