I think he is highlighting the small "whistle" devices you can have fitted to the car which is meant to make them nervous and so not come out in front of you on the road.
Yes Alistair, I meant those little devices, not much bigger than a referees whistle, that emit a high pitched note - inaudible to the human ear - when on the move. I put them on my tin-top when travelling up and down to Sheringham regularly to visit my aged mother when she was alive. The Thetford Forest area was teeming with deer and other relatives had had many near misses on the roads in that area. I never saw an animal after fixing the whistles to the car but that may be pure coincidence!
I am going to add a couple to the underside of the number plate box on the Plus 4 as there is nothing to loose and they can't be seen. I think that they cost £10 for a pack of 4.
