If you're cheap/privacy/FOSS focused like myself, I find the "PineTime" is largely the modern day Pebble watch.
It may not literally watch every breath you take while you sleep, but I haven't wanted that personally anyways.
Only real drawbacks are battery life is only OK (about a week or so depending), the IPS screen can be bright in the dark (though it's a nice flashlight) and it only has 1 meter of water resistance, though it seems well sealed enough to trust it if I fall into water momentarily. (And really, swimming/showering with watches is kind of niche anyways)