Whereas mental health wearables were once the brainchildren of niche startups, Amazon and Fitbit now want in. AdvertisementA few manufacturers of mental health wearables have aimed for a higher FDA designation, and the agency has signaled a willingness to consider them. AdvertisementA central goal of many mental health wearables is to harness physiological signs of stress. “There are no biomarkers for mental health that are used in a consistent way,” said Torous. We just don’t have a signal like that.”AdvertisementStill, mental health metrics have moved from niche companies into the marquee products of tech giants.