I tried wearing one on each wrist, and then just a smart(ish) watch. In the end I found I care more having about one nice real watch on my wrist, thank you very much.

Couldn't agree more. Tried a Fitbit. As soon as the novelty of knowing how far I'd walked in a day wore off, i found it annoying. Had to flick your wrist to make it wake up, which was never intuitive, so I found myself falling out of love with it fast!!