I want my kids to be able to walk to and from school and to be able to track them, see them and talk to them without buying them a phone. Cellular radio is just not medically safe as an always-on feature but an on-demand or emergency function would be good.
Not sure I get your point there. If you want a watch which updates the location of your kids in real time and is always available for you to call them (i.e. always attached to a GSM base station), it will need to include an always-on radio in the same way as a mobile phone (essentially what you are describing is a small basic smartphone attached to their wrist).