When I was looking for a used car for my parents my mother said to be sure it had one of those things on the back of the trunk that makes it easy to judge where the back of the car is when you park it. That was a new one for me. I did not know that was what it was for.
I have used them for parking aswell, I didn't install them for that though... and on my porsche 944 I turned on the lights so I could see the end of the hood when parking...