ramo@goodvikings.com:
I've recently started on developing a nagios plugin for tor, since a cursory google search didn't come up with anything I would describe as 'comprehensive.'
Please have a look at check_tor.py: http://anonscm.debian.org/gitweb/?p=users/lunar/check_tor.git;a=blob;f=READM...
It looks quite complementary with your probe.