When you work on a team, it's useful to have notifications go to a chat room where you can coordinate any necessary action. Reviewing a comment before publishing, seeing stories as they are written, getting notified of new orders are the kinds of things we like having in a shared room.
Chat support
Post Salt events into a Matrix room
In our quest to get all things into Matrix, we've also sent Salt events into a Matrix room. This is extremely useful to monitor the results of automatic highstate runs, individual commands, etc.
Post Nagios/Icinga alerts to a Matrix room

We just added Matrix notifications to an old Icinga server we have, because why not? We love having everything in Matrix...
Added D8 Rules support to Matrix API
As of today, the Drupal Matrix API module now supports sending messages to a room via Rules. Now you can automatically configure notifications to Matrix rooms without touching any code!
Added reminders to our Matrix bot
!remind me to respond to Bill in 2 hours
Yet another messaging platform: Why Riot?
People who know me know I can get stubborn when I get sold on a particular technology. For the past year, my favorite is Matrix, a distributed chat system that addresses pretty much everything anyone wants from a messaging system. The only catch? Not that many "regular people" are using it yet.