Why are doctors wary of wearables?OuraSmart rings have built-in sensors that monitor the wearer's heart rate and other health issuesWearable tech – currently dominated by smart watches - is a multi-billion dollar industry with a sharp focus on health tracking.Many premium products claim to accurately track exercise routines, body temperature, heart rate, menstrual cycle and sleep patterns, among others.Health Secretary Wes Streeting has talked about a proposal to give wearables to millions of NH...