I'm looking for something like Microsoft Operations Manager, only for Linux. Unfortunately, I can't figure out which search terms to use.

Basically, I'm looking for something that will periodically run a bunch of tests, to check that the various websites and mailing lists that I'm supposed to be hosting are up and running.

I could do it with cron, but it'd be nice to have some kind of integrated solution.

It would be nice if it was extensible, but it needs to support at least the following:

• Connect to an arbitrary website and check that the page returned looks sensible. By sensible I mean that it contains a bunch of expected text, rather than an error page.
  
• I'm not sure how to do this one without annoying people, but it should have a way to check that a mailing list is working correctly. Maybe just having a dummy mailing list at each domain, with only the test user would suffice.
  
• It should be able to check that various daemons are running and responding to connect requests. This means that I can check that my SMTP daemon, IMAP daemon, FTP daemon, etc. are up and running