Amazon's Smarthome stuff offers basically a bluetooth side-channel specifically for this purpose. It's called "Amazon Sidewalk", and they are already using it for Tile trackers, Ring Doorbell stuff (the doorbell even acts as a mesh point for this in some models)
Yep, eventually this technology will be worthwhile for folks with less scale to implement. Maybe Amazon will license access to Sidewalk. I believe Apple does a similar thing with their devices.