If you are serious about health tracking, get a device that specializes in that and knows what they are doing -- get a polar. They publish papers on the science behind their technology. Many professional athletes do heart tracking with polar devices. Even Garmin isn't as good being it is a GPS company first. If you want mediocre, by all means get an apple device. Their goal is to sell you stuff and keep you hooked in the ecosystem with a veil of convenience.

Fwiw, polar let's you tune the parameters of when to start and stop recording.