Inwas just looking at these a few days ago and I think there are two companies, Pebblebee and Chipolo. I read the Google network is opt-in (probably a good thing privacy wise but not great for tracking) so they’ll only ping off other phones that have opted in to the network. Samsung has their SmartTag, and Amazon has something as well.
Could you imagine going through security and then getting arrested for trying to carry explosives onto a plane?