I spoke about it a while back in the thread.
Its a small box that gets mounted on the rear of the car, spits out messages to my dash via CAN, thats it. Its not like OEM road car collision avoidance systems that will steer, brake, adjust suspension ect, its purely display only.
LEDs on my dash (well the SLM above the dash) will come on and change colour and flashing speed relative to approaching cars distance and delta speeds, when your about to be overtaken it will change to have LEDs show you which side, i can have a big arrow pop up on the screen ect.
Heres a bit on it
https://www.youtube.com/watch?v=EzpSy-eJRi4 For long races with a large number of cars all with various closing speeds, ie wakefiled 300 even like 6hr regulatory races ect can be great beneficial. If it warns you about one car that you didnt realise was there, its paid for itself.
https://www.youtube.com/watch?v=96vL7HMrExc This is the bigger (and much more expensive) system, instead of CAN based, the information is overlayed on the rear view cameras monitor, this system was built by Bosch and Pratt Miller for the GT1 corvettes racing in ALMS ect, races like 24hr lemans were the fastest GT cars are lapped by LMP cars with a very fast closing speed, obviously this system is priceless.
This system was also used for the first time in Australia during the Bathurst 12hr the other year, all the Fiat Abarth's ran it, because they were goign to be lapped by much faster GT3 cars.