Re: What?
It's possibly a licence feature. On the event of death, revoke licence so iWatch can't be resold.
Or it's a zombie app ready for the impending apocalypse. No pulse, but still moving.. Send GPS location to DHS/CDC for immediate intervention.
But I'm curious what you can't do with it if it's removed from your wrist. So if you take it off at night but just want to check the time, having to log in requires a higher level of consciousness than may be convenient.