Is there a way to to send notifications based on a participants activity?
Like in the Keynote, Apple included example for Music app where a participant adds songs to a shared queue and all other users get a notification about the activity.
Sending participant activity-based Toast Notifications
It looks like this is now available on the API with the postEvent(_:) method on GroupSession: https://developer.apple.com/documentation/groupactivities/groupsession/postevent(_:)-1dno2