I've played around with Simple Event Correlator, at http://kodu.neti.ee/~risto/sec/. It's a perl app (needs 5.6 or above), and is highly configurable. There's a lot of examples in the manpage. You can set alarms, actions to be triggered by certain events, etc. If you need something to monitor the system for disk failures, etc. and need something more than an updated status of what's in the syslog messages file, it might be better to go with that, instead of writing and testing your own code.

Oh, and there's also Splunk, although I can't say I've tried it. Just seen ads for it on slashdot and some other sites.