The results of several ambitious studies testing wearables as early predictors of for Covid-19 are in — and they suggest that data from devices including Apple Watches, Fitbits, and Oura smart rings may be useful for flagging some infections in people before they even feel ill. Recently published research from ongoing efforts at three high-profile institutions … indicate that wearables can detect a bump in heart rate or temperature, the most consistent signs that the body is mounting a response to an external threat before symptoms appear.