If I recall correctly, there is a U1 chip in the Apple Watch, right? If so, shouldn’t I be able to locate my watch with the Find my… App? That doesn’t seem to work for me. If it’s not (yet) a feature, what is the U1 used for? Is it only car keys in the future?
Has anyone found a good use for it?
I suspect it’s used in wearing a mask phone unlock, and possibly things like the magic band at disney.
Well worth it for the mask unlock if my guess is correct 
My older watch does mask unlock too. Agreed, it’s a great feature.
The U1 chip is a short range, ultra wide band radio transmitter/receiver used to locate other U1 chips, and can give both distance and direction information.
So I’m thinking finding phone, air tags, and other U1 devices with your watch, and I would suspect eventually finding your watch with your phone.
Sew an airbag into your child’s jacket and locate them.
Edit: one article mentioned directional airdrop, so standing in a circle of friends, you could “throw” a picture to the person to your left, etc.
The U1 chip seems to be one of those hardware features that have one or more stories we do not know about (yet).
I think that Apple had or has a lot in mind for the U1 chips and the technology. For some reason, they have not released much out in the open given its potential. I have the feeling that a lot exists or has existed behind closed doors that still has to be announced or has been canned.
A nice article on this topic:
EDIT:
From 2019:
I think that something has happened at Apple that slowed down the deployment process of U1 features and even U1 devices. I would love to know what this “something” is…
The patents go back to 2006, so it’s a slow revolution 
Recent feature: Series 6 Watch unlocks my iPhone. Could that be U1?
Unlocking the iPhone with the Apple Watch works as far back to Series 3, so they’re not using the U1.
Thanks everyone. I guess I’ll have to wait with the rest of you and speculate, until Apple tells us 