Guess I'm not the only one, and of course my personal site was down for the last three days because the domain registration had expired and couldn't be renewed on an outdated card.

I facepalmed.

But once my setups get a bit more complex I was thinking I'd build webhooks into an analytics server, and ping those from each server with a json request which includes health data for each's databases and other servers.

I'm no where near that so I'll probably sign up for the free plan on uptimerobot later mentioned in other comments.

Well this solution works for very many. Though for me it's mostly weekly for some sites, and daily for others.

Really??? Teach me! How do you manage doing that???