My team is finding @all to be way too much - people are being notified when they're off, which is a non-starter for us. I've searched the AppScript documentation, and all i'm finding is how to reply to individuals.
What I want: The ability to detect users that are Active in Hangouts, and @mention each of them by calling a bot. Is this possible?
Currently, this feature doesn't exist in the Hangouts Chat API - specifically, the spaces.members resource (is where I presume this would best fit under) & at all other resources.
I strongly recommend filing a feature request on their Issue Tracker, for now.