I'm thinking of getting an activity tracker (not sure what brand yet) to augment my workouts / cycling activity, but I have a question.

I see a lot of them monitor your sleep. How does that work exactly? I pretty much sleep anywhere from 6 to 8 hours a night, so sleep monitoring isn't high on the priority list, but I guess I'm curious about it nonetheless.

Thanks in advance for any info / comments / insights provided.

I've got a Fitbit One, my girlfriend has a Fitbit Charge HR. Lots of other trackers do sleep tracking, too, some of them better and some worse.

On mine, I have to press a button to tell it I've gone to sleep and another to tell it I woke up. And I have to wear it on this pouch on my wrist, normally it goes in my pocket. Needless to say, I don't use this feature very often. On hers, it just knows somehow. The weird part is she's taken it off and set it down before a shower, then forgot to put it back on, and somehow it knew she wasn't sleeping. Maybe time of day?

Anyway, these things use accelerometers to know when they're moving. The basic idea is when you wake up you're going to move a lot, when you toss and turn you're going to move a little, and when you're sound asleep, you won't move much at all.