well in California , if you can't use(it's blocked) or don't have a rear view mirror you must have mirrors on both sides. I also heard it is illegal to have a video screen visible to the driver while driving forward. highdesertranger
It is not a video screen it is a live view of what is going on behind you and is better than a rear view mirror because you have a wide angle view which assists you when passing other vehicles, unless you are too slow you can panic when you can see others catching up at speed.