Pokémon Showdown uses it for both – telling you your opponent moved, and message notifications when used as a chat app. It doesn't ask for the permission until

Pokémon Showdown uses it for both – telling you your opponent moved, and message notifications when used as a chat app. It doesn't ask for the permission until you start a game or send a private message, though. I think the original version of the spec required an interaction before the permission prompt when I implemented it – I'm surprised the restriction was removed.