New Delhi, Sept. 22 -- The days of tracking daily steps are passe. The two things that people want to keep a check on today are metabolic or cardiovascular age and sleep. These have emerged as better indicators of sound health and are tied to the current longevity obsession. Little wonder that the first thing people do when they wake up is check their smart watches and screen-less tracker apps to find how much and how well they slept the preceding night. But are these trackers accurate? To answer this question, I underwent a medical grade Level 1 sleep test using the Grael Polysomnography machine. I wore a Garmin Forerunner 265S, Google's newly-launched FitBit Air, the first generation Apple Watch SE and an Oura Ring 4 while undergoing th...