The Paxie kids wearable does so much, it's hard to keep count. Working with an app, the new device tracks location as well as surrounding temperature, heart rate, and fitness stats. It also pings you if your child goes past the boundary you've set. The band requires two hands to remove, so kids can't take it off themselves. Preorder for $175 has already sold out, but you can sign up to be notified when it's available again.