Nagalert is a project mainly written in Perl, it's free.
perl daemon/client for nagios-to-asterisk telephone notifications
SUMMARY:
nagd.pl and nagc.pl are a daemon and client system for monitoring network status via Nagios and Asterisk. When Nagios sends an unacceptable amount of problem notifications, Asterisk can respond by placing a call to the administrator's phone, using eSpeak.
USAGE:
nagd.pl should run constantly on your Asterisk machine, waiting for and handling input from Nagios.
nagc.pl should reside on your Nagios machine, and be executed each time a new notification occurs.
Please see commands.cfg.example and contacts_nagios2.cfg.example, as these need to be applied to your Nagios machine.