I have been thinking of something similar: I'd like a wearable that haptic taps me once every 10 or 15 minutes. Then I would check with myself if I am doing something that's actually interesting to me or just idling away.
I keep considering smart watches but if the goal is to prevent me from wasting time those could be counter-productive. Also I am sick of having products that require their specific charging dock.
You could probably build your own "start/stop a motion-sensitive reminder" app in a couple hours, though fine tuning it will likely take some time.
I regularly get a full week of battery out of it, and it uses a standard magnetic watch charger. The vibration motor is a bit weak though, and personally I rapidly grow to not notice frequent haptics so I can't use it for this kind of thing. But apparently watch-vibrations work for many.
[1]: it certainly has some annoying quirks and minor frictions, but they irk me far less than the quirks/etc in other watches I've tried. and I am MORE than willing to put up with it for the battery life and daylight-readable screen - I'm downright happy with it, and have returned every other watch I've tried in the past couple years.