Fitbit Air smart band from Google. A sports band that comes with two straps, one for the wrist and one for the arm. To improve the reading of the sensors. It can calculate pulse accuracy up to 99% if worn on the wrist and 100% if worn on the arm. Accurate in calculating sleep stages and its battery lasts for 7 days. Very comfortable, you don't feel like you're wearing anything. I used it for about a week. My price is 500, slightly negotiable. And for those who are serious, we won't disappoint them, God willing.