Power Meters / Powermeters (SRM, Powertap, Quarq, Ergomo, Vector, Stages, power2max, P2M, 4iii, InPower, Cinch)

Dunno. But I'm sure whichever Garmin Manbangle he's currently rocking 24/7 will know the answer. Or at least think it does - my Fenix 5X can't tell the difference between me:

1. Sleeping
   
2. Sitting at my desk at work quietly reading long and boring documents.
   
3. Sitting in my comfy chair watching the telly at home.
   
   

It claims I'm sleeping during all three. Not true. Promise. Well, maybe a bit.