getUserMedia and WebRTC Peer-to-peer connections APIs are not supported in iOS.
One of the reason is that at the moment efforts around WebRTC focus on VP8 video codec which Apple and Microsoft do not support natively. Support in the near future is unlikely with Microsoft pushing for its own standard.
Doing what you want on iOS requires you use a native iOS compatible solution like OpenCV which supports video capture. You can find on Google tutorials on how to implement a solution based on OpenCV.
https://stackoverflow.com/questions/23245359/video-streaming-in-ios-through-webrtc