It was a while ago, but I’m sure technology has improved for GPS accuracy, we bought one for our dog since invisible fence was impractical for the larger area we wanted to cover. Simply put, she found area where the GPS signal didn’t work so well and would sneak out. Under trees and brush, the GPS was just too weak to work. We wound up returning it.

Tried another one that used WiFi ranging, and that was far worse. It turns out a Ham radio operator down the road from us had a repeater on a tower at those frequencies, and interfered with us. His tower since blew over in a windstorm, but by then the dog was trained. Now she is too old to wander much beyond the yard proper.

Based on my fitness watch I bought this year, I think the technology is good enough now. This watch gets a signal downstairs under a roof and first floor. My original fitness watch was hopeless indoors.