Mine came with a double-din radio w/backup cam, but I hardly use it. It comes on when I put the car in reverse, and it works fine, but I just use the mirrors. I wouldn't have invested the time or money to install one.
I did, however install a rear-view mirror backup cam in my work van. I use that one constantly, because all the tools, equipment and partition in the back rendered my rear-view mirror useless. Now I can see if a cop is behind me
Not only that, it records front and back, so if some joker causes a wreck either in front or rear-ends me I'll have it on video.