There is some confussions, as OGG is indeed a container, but containers with vorbis audio inside have .ogg file extension, and are called "ogg" or "OGG" literally everywhere. Anyway, it's brillant codec by Xiph.org (the same organization, who gave us FLAC), and leading format of royalty-free, patent-free audio codecs.
Feature request - above obvious auto-recording of calls (SIP and GSM alike), which you're already considering for sure, it would be nice to have a (remembered) advanced configuration for codecs in use. IMO, most feasible way would be a text field, where user would put a string of text containing command-line parameters for codec, just passed transparently to used encoder (in addition to normal things defined by our application, like save path, etc).