What is unclear to me is whether a special phone app is required or not. One of the web pages indicates that it piggybacks onto the infrastructure for airtags/android tags (not clear which). Certainly, if I was building these, that is what I would do as getting a custom app in enough phones would be extremely difficult.

Having said that, the claim is also that these tags report temperature as well — but there is a field (personalized name) that could be used to transport that information. In any case, it is an impressively small tracker!