They work best for things that a human has to move, and since a good chunk of humans (at least in US/CA) have iPhones, the movement of the physical thing will be tracked by an iPhone fairly reliably. Any time the critter is outside the range of an i-device picking it up the location will be stale. There isn't really a way around that, since GPS/5G radios are a lot more power hungry than the occasional bluetooth pings an airtag broadcasts.