Apple should either license FirstBeat algorithms or better... design similar ones with same level of accuracy that don't require a chest strap. It baffles me how Apple harps on AW being for health... well after it was clear it failed on selling the AW as fashion... and still it can't, as a standard health feature, calculate VO2max. If find it hilarious that people demand sleep monitors -- like do they really not know if they slept well? and yet VO2max is a real benchmark one can use to find there true fitness level.
It's funny I run out every two years to buy the newest Garmin with the latest analytics just because it's cool. Until Apple does that I have no reason to upgrade my AW Series 0. I don't need a faster process to push out notifications or use ApplePay.
In tests, a calibrated Apple Watch is the most accurate activity tracker. https://www.cnet.com/news/smartwatch-step-counter-and-distance-tracker-accuracy/