A great little collar for peace of mind and motivation. My dog is very much a velcro dog but it's nice to know that if he ever did wander off I'd be able to find him. The bigger surprise was how the step tracker and social ranking feature made me way more motivated to walk him more and longer.
It currently only tracks walks and sleep. It would be interesting if it tracked more metrics/activities (eg. in a car, playing, swimming, etc.)