There are two other ways:
1) Write a script in Perl that telnets into the router, issues the relevant show int commands, parses the output and deduces the status. Then run that in a loop for a constant status monitor
2) Rig up something to suspend little photodiodes in front of the interface LEDs and connect them to suitable electronics to alert you if the light goes out.
Both are feasible, both would work but neither are worth it; just use SNMP!