To use it you need to sign up for a free account and login in each time you connect via a webpage (Shown in pic).
My iPhone is setup as a device as well as my MBA.
I'm currently at Kings college London and noticed when I'm out of range of my phone or switch my Bluetooth off, my Watch connects to a wifi hotspot.
I know the Watch can connect to known wifi networks that are logged in via the wifi settings page. But I didn't think it could login to a wifi network that required you to login via a webpage?
Is this an addition to WatchOS 3? Don't remember reading anything about it so far?
Nonetheless very happy it works on a public wifi network now! Can wonder around the campus and still send/receive texts etc