I had to take the rear bumper off last night in order to fit my "clear" rear light that I put in the oven the other week, and after reading about the parking dynamics sensor in this thread I thought I would take the chance, so I ordered it Sunday night and it turned up tuesday morning. Really simple to fit and wire up and works like a charm - the polystyrene pad over the crash bar insulates the sensor wire from the metal work by much more than the 3cm recommended in the installation instructions so no issues there.
I was going to go with two sensor wires (supplied in the kit) but it said whilst it would increase the range it would also increase the number of false alarms so didnt bother. The range is fine with just the one but I would be interested to see what its like with both fitted. The "brain" is hidden behind the trim at the back of the boot and the speaker wire runs up under the rubber trim at the side of the hatch all the way up to the side of the drivers seat and sticks with a little sticky pad.
Mate that helped me has been a vehicle auto electrician and installer for 20 years and hadnt seen these before and was very sceptical about whether they would work, so we tested it by me reversing at his legs and it beeped a good 5ft from his legs All in all a good cheap and tidy solution