Any script you install could be construed as an 'additional utility'. In any case, Nagios has a plugin (that doesn't actually require Nagios) that you can use to check several facets of a Oracle installation. It is trivial to write a wrapper to the check_oracle plugin that will run out of cron and email you if something fails, so you don't need Nagios proper at all.

Alternatively, you can install Nagios on a seperate host and have it run the check_oracle plugin from there, or call it via SSH. Lots of options.