Parsing Syslog and Acting on it, using other input too

Hello. I am looking for a way to do proactive monitoring of my network, what I am specifically thinking about is receiving syslog msgs from the routers and the backend engine would correlate certain msgs with output/data that i am receiving through SSH/telnet sessions. What i am after is not exposed to SNMP so i need to do it on my own. I am sure there are many tools that can do parsing of syslog and acting upon it but i wonder if there is something more flexible out there that I can just re-use to do the above ? Please point me to known public or home-grown scripts in use to achieve this. Regards, Sam