What is the best GPS watch for my elderly father who wanders?

Wide variety of Bluetooth GPS trackers. You could attach one to his shoe lace, or as a necklace. Baby monitor might work nicely. Only have alerts go when movement.

I doubt that someone who has memory issues to a point that they wander would be able to operate a GPS device.

There are devices that Dad can wear that will signal onto a software program on a computer or your Smartphone of his whereabouts. I know such a thing is made for pets, thus there must be something like that for humans.

When does Dad wander? Does he carry any ID when he goes out? Can you put an alarm on the exterior doors that will buzz to let you know that he is going outside? Nothing loud, or it would frighten him.

Does your dad have dementia? Can he understand how to operate a GPS watch?