In reply to Brass Nipples:
I did a search for "tracker bracelet for hikers" and not much came up. I suppose it's not that different to the SPOT device which I own (although I never set that up to give notifications of my location continuously for fear of draining the batteries). But I'm surprised that these GPS devices for children and the elderly don't seem to be marketed to hikers more, as they seem a lot cheaper than the devices like the SPOT ones.