Basically, I have the ARCamera which shows the video feed. I have other cameras that have orthogonal projections that show images. When the user presses a button, I want to "copy" the last frame of video onto a texture that sits on a plane, and this plane must fill the phone's display (just like a GUITexture would). Except, I can't use a GUITexture because I need to draw over top of it. I can't use a WebCamTexture because it is well known that this doesn't work on MANY Android devices.
Any suggestions?
So the video feed is not the camera image, it is another video source? - if it is the camera image, you can simply stop the camera to achieve what you are describing.
There is also a method by which you can register a Texture2D w/ the ARCamera to have this rendered w/ each frame. Our BackgroundTextureAccess sample demonstrated this approach. Take a look at the Readme file for instructions.