I'm not sure of the ethics on this.
I can track my computers, basically anywhere. Not all of them, but the servers and any workstations. Some years ago, someone stole a server from one of my clients. The person thought he had defeated the tracking, but obviously not. The tracker put us within 3 feet of the server.
Suppose I implemented such a tracking system on my Fiero. This is reversible, but difficult. If I later sold that Fiero, I would not be inclined to go through the trouble of removing the tracking. In theory, I could track that Fiero, until it was melted down. Hence the ethics issue.