How to get a phone notification if my VPS goes offline?

https://slrpnk.net/post/35723833

How to get a phone notification if my VPS goes offline? - SLRPNK

What are my options for getting alerts on my android phone if services on my VPS becoming unresponsive? My first thought is a simple app that periodically pings domains and gives a notification if any fail. Is there an open source app for that? Or something else?

Uptime Kuma has a number of notification options.

I just had to set one up because the Oracle free tier is hot garbage and needs resetting every day or two.

I used uptime Kuma with signal-cli for notifications - it’s been rock solid. I also have anotger uptime kuma that uses email as notification option to monitor my primary uptime kuma and the signal-cli.
+1 for Uptime Kuma, I use it with ntfy. If OP doesn’t want a self hosted solution, there’s UptimeRobot - essentially SAAS Uptime Kuma, but with a free tier.