I've found that the Garmin stuff actually integrates with healthkit pretty effectively. You can't make calls on (most) of the garmin watches, but they also have 30+ day battery (and in worse case, active GPS and music playback usage 72+ hours).

But I don't want to make calls or texts or be bugged by a fitness device.

Plus, the long battery life means you can sleep with it on without thinking about or caring about charging.