I have one on my wrist right now, and from the limited amount that I've played with it:

- There's a magnetic connector (like mac boks) that hooks up to USB. It doesn't come with a wall connector, just USB, which is a bit weird.

- It does indeed look like you need to press a button to start tracking sleep.

A big thing about sleep tracking for me is it being automatic. When I'm about to fall asleep, I'm often too sleepy to remember to press that button. It why I ditched my fitbit.

Other fitness trackers have automatic sleep tracking, even it's only heuristic based. For example misfit just has the formula of 'if not moving much for a large chunk of time in between these user configurable hours, mark that as sleep time'. That is a huge improvement.

The basis band seems to have a more advanced automatic sleep tracking algo. You guys would be probably interested looking into it.