The killer use case here, as I think most people have figured out, is figuring out where your stuff is when it's in a system you don't have visibility into. Like if UPS says it's "on the way" from NYC to LA or something, and especially if the airline isn't sure where your luggage is. It's just spectacular for that.

And of course where did I leave my keys and is my backpack in the car or at work stuff, but that's the obvious/advertised use.