I have a friend who’s ex a couple of years ago was teasing/harassing her with obvious knowledge of where she had been. The friend had a mechanic check every inch of the car for a gps tracking device. The mechanic didn’t find anything, but she eventually discovered that her car’s app had a “where did you park” function that the ex still had access to on her cell phone. My friend deleted the account and that ended that.
This sort of activity has been happening for longer than AirTag and Tile has been around, and at least with AirTag there is a way to find out that a foreign one is following you around. My friend ultimately wasn’t being tracked by a gps tracker, but if she had been, there would have been nothing to warn her that such a device was following her around.