Uptime Kuma
Uptime Kuma is a self-hosted monitoring tool like "Uptime Robot". Website. Issue tracker.
This integration allows you to monitor your system and send a SMS using ClickSend when it goes down.
Download the zip file here: https://github.com/louislam/uptime-kuma
Find the guide here: https://github.com/louislam/uptime-kuma/blob/master/README.md