I don't really need two cameras for the rear. The upper camera works the best and I could live with just that one. I purchased the 2nd camera to mount up front, but a couple of things caused me to change my mind. One is that the camera would be most useful mounted low, but then it's succeptable to damage. Pretty much anywhere up front, the camera can be damaged and I drive around on dirt roads a lot, following people. A little bit of dust from following someone and the lens is covered and useless. But other than that, I can see some interesting places to mount it, as least just for fun.
So, I mounted in the rear to give me an alternative position. One of the problems with any camera system is there's little to no depth perception. When a camera is mounted up high, you get a great wide angle view and nice and far back, but the image is 2D so, when you're looking at the ground behind you, a 3 feet hole can look like flat ground. A lower mounted camera gives a different point of view. I wouldn't say it's absolutely necessesary, but it gives me a use for the 2nd camera. And being as the rear is the ultimage blind spot, I'd rather put both cameras to use there.
Good find on the Audiovox page. I never thought to look there:
Here's a list of their mirrors:
Welcome to Audiovox
Oddly enough my model number RVMPKG4 doesn't exist anymore. Probably discontinued and replaced with this one. I see it has duel speakers. Not sure if there are any other improvements:
RVMPKG3
That's the bad thing about buying any electronics. It's outdated the moment you buy it. One thing I've found not so great with this set up is I was driving to work in a major rainstorm and once you get the camera lens wet, it's pretty much worthless. You can see, but not very good. I've been using it as a rear view mirror while driving. It's actually really only intended to be used when backing up, so it's just as easy to get out and wipe the camera off before you use it. I think I might try to mount the lower camera inside so I can benefit from the rear wiper in rainy or dusty conditions, though.