WarVOX is a suite of tools for exploring, classifying, and auditing telephone
systems. Unlike normal wardialing tools, WarVOX works with the actual audio from
each call and does not use a modem directly. This model allows WarVOX to find
and classify a wide range of interesting lines, including modems, faxes, voice
mail boxes, PBXs, loops, dial tones, IVRs, and forwarders. WarVOX provides the
unique ability to classify all telephone lines in a given range, not just those
connected to modems, allowing for a comprehensive audit of a telephone system.

This requires iaxclient, lame, and rubygems.
Once dependencies are in place, open a terminal and, as root, run:
  # gem install rake sqlite3-ruby mongrel
and everything should be ready to install WarVOX ;-)

To run WarVOX at startup use something like this in your rc.local:

# Start WarVOX
if [ -x /etc/rc.d/rc.warvox ]; then
  /etc/rc.d/rc.warvox start
fi

and something similar in your rc.local_shutdown to stop the service.
You can access the web interface at http://127.0.0.1:7777/ or at the port
specified inside /etc/rc.d/rc.warvox