They use a 'Sentinel' system on Dakar racers to warn of a faster vehicle approaching, but that's with wide open spaces and at lower speeds. I'm not sure the drivers would be able to react in time with these beasts.Seeing the two Audi crashes coud have been avoided, I think it would be a good idea to implement some sort of aproachwarning on the cars. Since every car should have a transponder anyway, why not use the info incar? On a sprint race the engineers give that info, but in an endurance race with so many participants it can get hard to get a grip on. Especially if after some minutes it still wasn't clear which car is out. A mere amped up parking sensor wouldn't work, because the walls get closer anyway. So if you equip the GTs with an LMP warning, acoustically or visually, maybe at least the second accident could have been avoided.
Sorry for the incoherent mess, I might have followed the advice to grab a new beer a bit too often.