Kazoo is a flexible cloud PBX platform, released under open source, developed by 2600hz.com, with the telephony engine built using Kamailio, FreeSwitch and an Erlang controller, all wrapped nicely with a web management interface, doing all sorts of things from account management to billing and monitoring.
If you want to start a cloud telephony business or get into this market as a reseller, KazooCon is an event that you should definitely attend. More details about the conference are available at:
Kamailio incorporates a module with the same name, kazoo, but besides it, the developers from Kazoo project contributed a consistent effort in advancing the presence and database modules. Therefore expect to meet a lot of Kamailio friends around at KazooCon and participate in many interesting discussions.