Tracker/Phone Watch for kids advice and recs

I have a third grader who we started to allow more independence; he is allowed to bike or run around within our HOA with friends unsupervised and is permitted to sign himself in and out of aftercare to go to after school activities taking place on school campus.  I trust him but would still like a bit more information as to his whereabouts and a way to get a hold of him.  I heard about those watches for kids that allow for gps tracking and ability for him to call a few pre-programmed numbers and for us to call him.  I heard of Gizmo and that there are others, but don't have details.  Anyone's kid has a watch like that and if so which one do you recommend or don't recommend and what should I look for when picking?  The main features are ability for us to call him and him to call us and GPS tracking, though it having steps counter and heart rate/beat monitor (to replace his current health watch) and some games to make it fun  for him will be great too.  Cost is not really a concern so I want to find one that is the best fit for him and our needs and will last him about 3 years as he won't get a phone till he starts middle school in 6th grade (which is customary in our area) so we will rely on this watch for a while.