I used to think parking sensors were a waste of money as I can park without any problems.
One day I went out to the car (about 2 years ago) and it was really frosty. I got in the car and turned on the heater etc, and scraped the frost off the car widows. I didn't bother with the rear one, as I thought the heated rear would take car of it.
Little did I know, that in the 30 seconds I got in the car and put my seatbelt on etc, a van had come into my car park and parked pretty close behind me.
I revered out, and CRUNCH - reversed straight into him. It wasn't fast, but it was still enough to smash my bumper - and his!
There was a shortage of Editon 30 bumpers at the time, so I had to drive about for 5 weeks with a smashed bumper. I claimed through my insurance and it cost over £1200 for his bumper and mine.
I ordered a new car on Saturday - £400 for parking sensors. They would have saved me a LOT of hassle, a big excess, and some embarassment! Now it seems like an obvious choice!!