I have the Samsung Gear 2 Neo, and tried building an app to record HR all day sampling once per second. A full battery lasts about 12 hours in this condition. H

I have the Samsung Gear 2 Neo, and tried building an app to record HR all day sampling once per second. A full battery lasts about 12 hours in this condition. However, the heart rate monitor subsystem crashes fairly often, and gets very inaccurate with pretty much any arm motion. So not super useful. Basis, Amiigo (not yet for sale), and even Epson have wrist-based trackers which claim some form of continuous heart rate monitoring. The Epson in particular seems interesting, as they developed the sensor in-house with a focus on power management; they say it can record continuously for 40 hours.