Hi! I would love to help you with this project. I am an IOS developer and UI/UX designer from Sweden. My speciality is developing apps from the ground upp with my own backends and APIs. I do all my applications universal if requested, that means that they are developed for both iPhone and iPad.
I actually came across a good video and audio calling SDK a couple of weeks ago that i implemented in an app. The SDK is called linphone. If you want i can help you set it upp in you app. you will have to stand for the SIP server but i will set everything up for you so your just upp and running.
I hope i would get to honors to help you with this project. Please get in touch with me so we can discuss more.
Best regards, Pontus Jacobsson.