Asterisk-mrtg.pl
This script ( see that download link far to the right of “An MRTG script to allow graphing of concurrent calls in asterisk” ? ) is good, but I think it could be somewhat better.
That’s because in the version of asterisk we have on our system, the Manager interface outputs the channel in upper case not lower case: SIP not sip. So we had it configured for “sip” and it wasn’t returning anything. I changed it to “SIP” and it’s working again, but a case-insensitive flag would help me 