Bluetooth with your own mobile works for at least 50m (day in the car and in a direct line).
But if the cat walks a few kilometres to the next village (or takes off to Polynesia by plane), all it needs is another Android user nearby who has Bluetooth on, then the last known position of your cat will be displayed on the map.
Since cats don't normally carry smartphones themselves, the cat won't receive a security alert that it's being "tracked" by your tag.