Each phone number being called out to needs to be able to be set to either forward with confirmation (i.e. person recieving call presses keypad number to accept call) or direct forward (i.e. no confirmation - if the phone is answered by person or machine caller is connected live immediately). There also needs to be a setting for how long each number will be rung with out a connection before going to the next number. Also if there is confirmation required for a number there needs to be a setting for how long the incoming caller has to confirm the call.
The interface has pretty much been created. Just need someone to edit applets that are all ready there.
http://www.openvbx.org/docs/api/2010-06-01/plugin/ gives info about APPLET PLUGINS
http://forum.twilio.com/twilio/topics/support_for_ringback_tones gives two different strategy for creating a ringtone effect