Everybody is talking these days about how the new cars will be fuel cell based, will drive without any human help and basically will change the world. What they are doing here is very good for sure, because they go away from oil towards renewable energy sources but I am sure that if you want to really change the world you need to produce a paradigm shift of a bigger magnitude. Something similar or better then the Segway will do, but would help to be a little more successful 
What they are missing from the big picture here is the maybe 200 millions cars which are already on the planet and the associated industry interests which are very big (money speaks here). If you really want to change the world, you need to do it step by step and in small increments. This way, the world won’t notice is getting changed
Back to technology now. We have parking sensors, wirelless communication ( I think bluetooth 2.0 will do in this case), and we have from the aircraft industry TCAS (Traffic alert and Collision Avoidance System). Obviously the scope of the system I am dreaming here is to try to avoid the car crashes, saving lives, and repair costs. This system needs to work even if my car is the only one which has the system installed.
So we put around the car 8-10 parking sensors (would be great to have a detection range of around 100 meters. don’t know if is possible), some communication device, some logic onboard and an interface to the audio system in the car.
If the system detects a possible collision course it can announce the driver about the danger and what he needs to do to avoid it.
Is common knowledge that every car buyer has 2 momments of happiness in relation to his (her) car: when he buys the car and when he sells the car. We need to keep the cost of the system low, so for the existing cars we won’t interface the controls of the car with the TCAS, we will just inform the driver what can he do.
Now, if the system is successful, the next step would be to interface the system with the controls of the car, giving the option to the owner to bypass the driver in case of an emergency.
The final step would be when most of the cars are having this system on board to forget about traffic lights and just automatically syncronize the traffic, allowing cars to pass from one direction to another without stopping.
In the mean time we can push for fuel cells, maybe solar power, biodiesel to change the way the car is powered.
They should first increase the over all efficiency of the engine; automobile engines are on 24% efficient at best.
Do the math in BTUs.
This site deals with the improvements of automobiles in the world.
automobile