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?
Ntfy can send/receive notifications to/from the phone. You can selfhost it or use a public instance. For the healthcheck app, consider Uptime Kuma as it has ntfy integration. But a simple cron script that monitors + cURLing ntfy when it fails could also be used.
Ntfy is a good lightweight option indeed.