When it comes to high-tech features, luxury car drivers get all the love. It’s true for massage seats, neck warmers, and self-parking systems. And it’s true for head-up displays, which project information onto a car’s windshield, so the driver can see how fast she’s going and what song is playing on the radio without taking her eyes off the road. The technology has been in fighter jets since the 1950s, and auto makers have been toying with it for nearly three decades. But the cost of the technology has confined it to the luxury market.