Service monitoring daemon

[Mark]

Hi all,

Is there a service or script that periodically monitors if a given service
on a machine is still running and if not restarts it?

Example: 
if "ldirectord ldirectord.httpd.cf status" does not return something
containing "running with pid",
	 then call "ldirectord ldirectord.httpd.cf restart"

I know this would be a pretty easy 1- or 2-liner into cron for each service,
but maybe there is something that already does this a little better with a
config file for expected results and actions to be taken if the actual
result is different for each service.

Thanks,

MARK