H10 works perfectly well. Also does not drain much energy.
Haven't specifically measured, but remember have worn it for hiking whole day and didn't see much difference (without GPS!).
Update: used recorder app
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
H10 works perfectly well. Also does not drain much energy.
Haven't specifically measured, but remember have worn it for hiking whole day and didn't see much difference (without GPS!).
Update: used recorder app