Grafana + Prometheus dashboards can be quite addicting or useful. Noted.lol put together a nice tutorial for getting started.
For most of my services though, I simply use Uptime Kuma which then sends an alert to Gotify when my services go down or whatnot, Gotify then instantly notifies my phone so I can be aware. It helps keep the spouse happy when their go to service for some reason crashed. :)