handy if you lose something like your keys somewhere in your home.
As I already mentioned in a previous post, the ability to detect not just "left" or "right" but also "above" and "below" will be crucial. I live on the fourth floor of a four-story building, and if I leave my keys at my friend's place on the second floor, it could tell me "your keys are 10 feet to your right" but if it fails to include the crucial message "and 20 feet below you", then that "10 feet to your right" will be pretty useless.
Here's another example: a mountain-climber loses his or her keys when they're 700 feet up and then realizes that his or her keys are missing when they're 900 feet up. Sure, the keys might be 70 feet to their left, but without mentioning that they're also 200 feet below, the AirTags are going to be pretty useless.
As humans, we move in three dimensions, not just two. I hope Apple took this into consideration.