We have it integrated into our incident management system. We also have it integrated into a homegrown alerting and monitoring solution, where it does some automation and self-healing behind the scenes.
We are working on an email integration for our service desk, similar to how xMatters themselves have it set up.
It provides incident notifications, subscription notifications, etc.
We use it for triggered tasks or events. Whenever a high ticket is created, it automatically notifies whomever is on call for the ticket that is assigned to a particular group, which was really one of our first use cases for it.