Xiaomi and Amazfit appear to be preparing an update for a number of their wearables that will allow the devices to take their user's temperature. The fitness trackers that could end up receiving such a firmware update include the Mi Band 5 and other SKUs from the Mi Band line and the Amazfit Band 5, which comes with blood oxygen level measurement.
https://www.notebookcheck.net/Xiaomi-Mi-Band-5-and-Amazfit-Band-5-feature-on-list-of-fitness-trackers-that-could-soon-be-able-to-take-your-temperature.499217.0.html