I have actually thought about something like that, where I would secure a micro camera to the inside left, of my helmet visor, and having it feed the video into the RF box, but I would be able to take snap shots, and zoom with the camera and look at far distances..
I don't have it attached to the helmet yet, but I have a camera that feeds to two lcd displays. one would go inside the helmet and the other inside the rangefinder (i have a hollow rangefinder). The camera is just going where the calc chip is in the back. this way i can see behind me at all times