For those wanting a geofencing alert system that works way better than Tile, try Chipolo. They make key fobs and a slim wallet tracker called Chipolo Card. The card had saved my butt many times because it alerts me as I’m waking away from my wallet. Left my wallet in a few places before - was able to walk right back and get it. This system is ideal for me because I don’t want to wait until I’ve lost something before I start searching for it.
Also, no subscription is required to use geofencing alerts, unlike Tile.
If Apple has not implemented this feature on Airtags it would be baffling as to why not.