Isn't there a bunch of good monitoring solutions and all you need to configure is, X should be reachable, or it should answer with a HTTP status code 200. And that's the needed effort per service?
Idk which monitoring software is best of as today, here's a list: https://github.com/awesome-foss/awesome-sysadmin#monitoring--status-pages
I guess there's lots of edge cases, though. Testing for example whether some web form still triggers an email in your inbox is probably something that requires custom logic.