No benefits at all, only privacy loss
I've been in one accident in my 9 years of driving. A crazy woman gassed it in a parking lot, lost control and smashed into me. No amount of beeping of flashing would have helped. Perhaps making turns onto main streets in low visibility might benefit from some sort of alerts, but useful alerts that could come from automatic detection systems would have to be mostly preemptive and I don't want a dashboard full of potential warning lights.
The technology for self-driving cars is possible, I'm sure, but is extremely far from being even remotely possible at this point. Even it were possible, there would be entirely too many issues. The country where this would be implemented would have to go through massive social restructuring. The legal system would have to require little to no liability for these automated systems. The millions of car enthusiasts out there would have to willingly accept their cars becoming toasters, mere appliances.