Ask HN: An inexpensive way to find my father (with Alzheimers) if he gets lost

Looking to find a reasonably priced solution to find my father (who has alzheimer's) if he gets lost. Some info:

* He's 75, lives in urban Vancouver, in his own apartment in an independent-living seniors centre

* He doesn't have or want a smartphone

* He hasn't gotten lost yet

* He's pretty stubborn and probably wouldn't wear something he knew was for this purpose

* Battery consumption is important, as I'd have to do the recharging for him

First thought is a "normal looking" smartwatch with GPS and mobile data. I can program Android, so could make a custom app that pings out his location on a timer, or listens for a push and then send out his location.

Maybe use SMS only with a pre-paid sim?

Any recommendations on the best watch? Alternative to mobile data?

Other ideas? I see there are shoe insoles as well...

Thanks