I’m liking the specs of Trackr.
This avoids the deal-breakers I’ve seen—it’s not a one-year subscription for example, or a one-battery-life subscription, you can replace the batteries yourself.
It supports short-range location directly from my phone (Bluetooth). It supports distance measurement (not sure how accurate; but one of my use-cases I want to try is setting an alarm when my camera gets too far away).
There’s one area in which, to be really good, there has to be one winner—or at least, a dense enough crowd of each of several competitors to be useful. It supports long-range location via crowd-sourcing; anybody running their app who gets near my tag will send the GPS info to their servers anonymously. Something like this seems unavoidable, because the cost and battery-life consequences of having the discreet little tag able to communicate over long distances seem intractable.
Dunno if their app is good enough, or if the device is actually good enough, etc. But I don’t yet know what “good enough” is anyway; I need experience with a device in this field to get my preferences clear.