20 foot class C here. Works very well. I bought a cheapo license plate camera & wireless monitor for $100 Canadian at a local store and first mounted it on the license plate but it was almost useless there with very poor sense of distance. Then I mounted the camera high up at the top (inside) of the rear window, aimed down so the back mounted spare wheel is at the edge of the fired of view. I can see the kayaks on the trailer behind and without the trailer I can back up to inches from a post.
I connected the power wires from monitor and camera to the house DC because it was easy and I can turn it on anytime I want want with a switch mounted on the driver's seat base. It is useful when pulling the kayak trailer and even when camped sometimes, as when the fox goes behind the MH and we don't want to scare it by pulling the curtains.
At home we have a little $70 Dlink DCs930 wifi camera with which I can see the living room on my phone or iPad, using local wifi or over cellular Internet when away from home. It could be used with a wifi router in the motorhome but I personally would rather have the dedicated monitor than fool around with the iPad app when I want to use the camera.
I recently bought another camera and monitor (wired video), hoping to use it for backup view and the wireless one for side view.
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2004 E350 Adventurer (Canadian) 20 footer - Alberta, Canada
No TV + 100W solar = no generator needed