Apple

There are standalone GPS trackers that report its location via a cellular connection. Typically they are used to track pets and the elderly in case they get lost, you might be able to find them relatively cheap at pet supply stores, but they do require a continuous paid subscription to work. Though they do have the benefit of working anywhere that has a cellular connection without relying on having specific brands of devices nearby.

If you don't need remote tracking, GPS trackers that only log to internal memory also exist. Those don't require a subscription because they only need to listen for GPS signals and not transmit.