Get a notification when a service is back up?

[jaeti01]

Hello,
I just picked this project up as it seems very simple to setup and doesn't require a lot of overhead. I also appreciate that Adam maintains a docker version (though it doesn't seem to run on the latest version).
My question:
I use pushover for notifications. That works well when a service fails.
What I didn't get working so far is a notification (lower priority) when the service gets back up. How do I achieve that?

I use the docker image, that runs v0.90.78

Thanks!