I have a smart-watch but not for the fitness features at all.
My TicWatch Pro runs on Wear OS (formerly Android wear) which means it can support the Xdrip+ watch-face that displays my glucose readings from my Freestyle Libre sensor, which are collected via an NFC-to-bluetooth transmitter stuck over the top. In theory, it can do this without needing my phone to be nearby, though in practise it's actually pretty flaky for this. Nonetheless, being able to see my latest glucose readings at the flick of my wrist rather than having to use my phone is really helpful. Especially while I'm driving since any interaction with the phone while behind the wheel is dubious if not outright illegal in most circumstances.
If it weren't for this, I wouldn't be bothering with a smart-watch as I rarely ever use any of the other features. As someone who takes his watch off overnight anyway, popping it onto its charger alongside my phone is no big deal, so the just over a day battery life isn't much of a concern.