I believe it was bluetooth, I'll research and edit I found it on a spec page at one point.
# can you use two camera systems at once? Will they interfear with each other or is there a way to set the channels? Thanks
* It should be fine to have two cameras mounted on separate vehicles, as it is rare that both vehicles would be in reverse at the same time. However, the cameras will interfere with each other if both of them are active at the same time. The result is that the display will get confused about which source it should read from.
That is from the VR3 camera system which is the one I looked at last year, I can't find anything about "peak" which is the one you linked.
http://sewelldirect.com/VRBCS300W-wi...kup-camera.asp
And i'm pretty sure I read somewhere that it was bluetooth but I can't seem to find it now.