I have been tasked with investigating the feasibility of writing an iPhone App to access our internal VoIP/SIP systems.
I've never coded anything close to VoIP before. Are there any open source VoIP/SIP libraries or examples in C or Objective-C?
An iOS App that I can skin and add our required features to (mainly UI related) would be the holy grail here.
Although it's rather old thread, for reference I add here also pjsip: http://www.pjsip.org that has a quite mature iOS port nevertheless it is written in C and its API is also in C.
UPDATE as of 06/2021: please note that this answer was originally written 9 years ago. I completely off from VoIP development now and can't take any responsibility wether pjsip is still working on iOS or swift.
