Nike Fuel bands, how do they work?

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One of my high school students ask me about these. I am not sure why because I don't have one I guess since I am a teacher he just thinks I know everything wink:
Anyways we looked it up and the Nike website stated that you wear it on your wrist and it tracks your movement through out the day. Well I am a teacher's aide (because I just moved to Texas and didn't have my teaching license here) so I sit a lot but I move my hands a lot with my butt always seated.
Does that mean its going to track my hand movement and think I am moving my whole body? It wouldn't be good for me if that's the case because it would give me an accurate number, is that right?