That's starting to look like the business.
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I occasionally require a reversing camera (when hitching boat or camper trailer) (our drive is on a wicked slope) and the kids are still surprisingly unreliable in marshaling!
I looked at a number of wired solutions to installing an (ugly) camera and was reluctant to install anything that might use more Defender screen space. My epiphany was to use an "action cam" - I am using a Garmin Virb that we use for the sailing action - this mounts onto the roof-rack and provides a wifi video stream to either iPad or iPhone for the few seconds required.
The solution doesn't engage automatically (a few seconds of planning are needed before and after to connect camera to the roof, start up the software) but the video is sufficient and I required no additional hardware. It has also been fun to capture a few action shots on the truck in motion on the muddier trails. Both the Garmin and GoPro alternatives provide the wifi connection to iOS and android devices.