Hello,
I'm currently working on a calling card application written in Ruby, just a hobby, I currently have it on a usable state and I thought I would post it here in case if there is someone interested.
It uses mod_nibblebill as the billing/rate engine and FSR (FreeSWITCHeR) as the event socket library.
Here is the url of the project:
http://github.com/diego/freeswitch-card/tree/master
You can find a clone of the project on my FreeSWITCH contrib directory too.
http://fisheye.freeswitch.org/browse/FreeSWITCH/contrib/diegoviola/
Regards,
Diego