I've tried a BT tracker couple years ago, and I just can't recall the name for the best of me. It was in a coin shape(possibly Chipolo or Trackr), and it was so underwhelming that I just don't even remember its name.
My main complain about that tracker was it's inconsistency--after dozens of tests, in different places and settings, the only conclusion I draw is the inconsistency. Under the same setting, sometimes it works and sometimes it simply doesn't, and there is simply no valid explanation. The worst is the limited app or the features lack thereof, the whole thing is just dumb. Meanwhile, I got some El Cheapo Chinese 'proximity personal alarm', and it works like a charm. However, due to it larger size, I didn't bother to continue to use that.
I sure tech has advanced enough nowadays, and hopefully something better would have surfaced by now.