Ok, sure it's a great safety feature to make sure the kids arrive at school or soccer, but you can certainly dream up all kinds of other uses that can really compromise privacy. No doubt suspicious spouses will find ways to use this to track wayward partners, and kids will find ingenious ways to confound their parent's efforts to put this electronic leash on them.
This sounds like one of those ideas that worked well in the focus groups, but am not sure it will turn out that way in real life. Having conducted countless focus groups over the years, I know how this plays out in the confines of a research setting, but I just see more potential for misuse than good use. Time will tell.