[highwaylights]

You can try this on yourself pretty easily.

Two fingers under the watch (far enough to cover the heartbeat sensor) and a swift upwards yank will pop the strap underneath and it’ll lift right off.

The thing is, if someone has your unlocked watch, what can they really do? This is a question I’ve never really known the answer to and doubt you ever would know clearly.

Certainly banking apps don’t seem to have a lot of functionality on watchOS, but I’m unsure to what extent being signed in on an unlocked watch is the same as being signed in on an unlocked phone. Can i authorise a new phone just from the watch? I can certainly get 2FA codes to the watch, so the answer I guess is maybe.

[garblegarble]

Well I'll be damned, so you can. With a watch alone they'd have limited access, but if you steal somebody's watch without the watch realising it's been removed & also steal their phone you can almost certainly unlock the phone with the watch (my partner + I use that all the time when driving... they pick up my phone, show it only their eyes, and the phone assumes it must be me wearing a mask and so it uses my unlocked watch on my wrist to unlock the phone).

The good news, however, is that you don't appear to be able to use the Apple Watch mask unlock feature to pass further Face ID checks deeper in the system once unlocked, so your banking apps & password manager is safe... but your messages & e-mails are not...