Looked at fitbit but not sure about all the tracking features, I think DD especially could become a bit obsessed. Also people are saying on another thread that they aren't that comfortable, the straps break and can't be replaced.
Basically my kids want to be able to tell the time easily during the day in secondary school without having to root around for their mobile phones in the backpacks. I would just get them plastic swatch watches but they really want digital. Any ideas please?