I,m just wondering how accurate are those trackers. I owned xiaomi band 5 (i know, the cheappest possible option out there) and I wasn’t pleased . Now I have got polar vantage m with sleep tracking and nighty recharge feature (it’s basically like whoop, it measures resting hr, hvr, breath frequency) and based on the data it tells you if your body is prepared for a hard workout (or that you should let it go and take same rest). The main con is lack of integration - you can sent only activity data to trainingpeaks, strava or google fit. Still I don’t believe on accuracy of that divices. Sometimes I feel like shit and polar says me - it’s you day go and crash it, and other days I feel normal or even very good and polar shows me that I should rest.