Challenge Friends to an Activity Competition
The Apple Watch tracks all of your activity, and now you can upgrade that by competing with friends in Activity Competitions.
This lets you set up a 7-day challenge against a contact so that you can get that little bit of extra motivation.
It's a cool way to keep going when you might otherwise slack off at the end of the week.
You both need the Apple Watch and one person will need to invite, while the other accepts.