There are several threads here on the rear view cameras. There are the race cams which are VERY pricey but give the ability to record. The other types are the display only types. There you have a choice of mirror version, 7"/3" types or the small monitor types. All of these are of pretty good quality and you have to realize that these are not good for distance judging as most use a fish eye type lens i.e. the passenger outside mirrors disclamer "Objects are closer than they appear". They are good for judging whether someone is infact behind you.Night vision is O K but not great. They have a button that will improve the night vision, but not all that great on a non lit roads, works great in a parking lot.
I have an old Pep boys version that works great. It made it though two years and a lot of rain days, many hand washes and 4 automated washes. Unfortunately I found one that really got the truck clean, and I was getting tired of doing the washing.
For Christmas, I got a new one and it has an upgraded camera with a wider range of vision and is digital. The difference is that it actually has a transmitter between the camera and the tail light hook up. I need to work on that connection as it is a little problematic right now. On an earlier post on this thread there are several options for you to chose from. Some are Hong Kong, some U S, some Ebay, some distributor houses.Take your choice.
You have to mount them high enough to see what you want to see, which is not only cars directly behind you, but cars off to the side as well. I like the ones with the 7" screen because they give you so much more that you can get from the unit. I like the combination of a radio, DVD,CD, IPOD, GPS, etc. etc. because I need a radio/music system anyway. Yes you still have to buy a camera. I plan to use a good quality camera and will build an enclosure on the rear of the spider sortof like the Nascar guys have and use it like a mirror. If I want to record, I'll do it inside with a camcorder or digital camera in video mode.
The neat thing on the ones mounted on the rear license plate is that it barely captures the trailer hitch and I can load the trailer to the truck without getting out 15 times to line it up.
Bill