I want to get Apple Watch unique id. Is there anything available like UDID or unique identifier for developers?
There should be a way with Xcode 8...but I can't find it.
My solution for now: launch "Accessibility Inspector", click "Start inspection follow point" button (the one in the middle, kind of cross-hairs), click in Xcode on top of the UDID value and then copy the UDID from the inspector shown values.
It turns out you also have to add the UDID of the Apple Watch to the Apple Developer Portal, and update your Development provisioning profile to include this UDID.
The UDID can be obtained in Devices window of Xcode. After pairing, the info of the Apple Watch will automatically display below the info of your iPhone.
At the time of writing, this seems to be documented nowhere, and the error message on the Apple Watch wasn't particularly helpful. So I wish this try-and-error lesson would save you some hassle.
Open XCode.
Under the menu Windows > Devices
select your iPhone (must a registered device)
Below the info about your device you will notice an headline "Paired Device Information".
One of the data provided is "Identifier". Copy the related value in your registered devices in the Developer's Portal and you are ready to go.
You mean you want to access it via code written in your app? I don't think this is possible. I know it's not possible for iPhone. And apple do not accept apps that access the UDID. seems you're out of luck.
http://www.macworld.com/article/2031573/apple-sets-may-1-deadline-for-udid-iphone-5-app-changes.html
来源：https://stackoverflow.com/questions/29275418/how-to-get-apple-watch-unique-id-or-udid