After scraping the front plastic bumper of my 87 Chevy Turbo Sprint (so how many Viper owners also have one of these??? haha) on a rusty column, I came up with this method: (NOTE: if the column had been nicely painted, I don't think there would have been any damage.)
HANG a piece of round foam pipe insulation from the column or wall.
When your bumper/fender touches it, it will roll and you will see this.
Being foam, it will not damage your paint (unless you have a black car and well, you are already Living in Hell - and YES, mine is black...)