It works!! Streaming video from the Pi directly over USB to my iPhone. The video was recorded using a test app I made. No audio.
This was a USB camera. It also works with the Pi camera module.
I’ve ordered a 222 degree fish eye camera module for the Pi. I’ll be trying to wrap the image from that via MJPEG from the Pi to an immersive 3D sphere projection viewer using ThreeJS or Objective-C.