I'd like quite the opposite - a built-in version of those noise-cancelling headphones - that the car's speakers actively abate the noise outside.

Then, rather than blast the ears with roadnoise and expensive directionalmicrophones that will foul in weather and dirt; use a local (500m) transponder inall cars; and let a car-onboard computer recieve: "heading/time" at .1 secondintervals broadcast on this car-transponder-frequency. Then an onboard computer, using vectors and momentum would have fair warning of a potential collision - being able to warn the driver - by blowing air at the driver'shead from the direction of the momentum collision stronger and stronger, andan LED indicator. After some training for bends and traffic situations, such a collision monitor would be much more accurate than trusting humansto hear.

With car sound, i'd like the same thing that jet aircraft's have, the ability tosound up and speak with just the left-rear seat by using conference-room technology that amplifies voice-sound gently in the rear seat. Or the abilityto switch to an engine-compartment microphone to listen to how she's running;or the ability to hear the baby in the back seat's burblings.