I built a pretty simple command line application (glorified python script) years ago that sends messages into a specified matrix room, and intended for use as a basic server notification system. Only recently posted to github (because a friend asked me to share); see: https://github.com/mxuribe/howler
Like other sys admins and devs, I had used email notifications for years to notify me whenever *stuff happens* on a server (like a job ran/completed, some storage device is low, etc.). But when matrix came out several years ago, i really liked the concept, became a bit of a matrix fanboy, and built a little script to leverage - nowadays, all of - my server notifications. Again, pretty basic/not sophisticated, but it scratches my itches.