HD Radio is on a roll: It's been recently announced that the number of new car manufacturers offering HD Radio as a built-in option has tripled. Or more specifically, the numbers have climbed from one (BMW) to—drum roll, please—three, now that Hyundai and Jaguar will have HD Radio as an option on at least some 2008 models. Jaguar will have it on the redesigned 2008 Jaguar XJ (shown here) and Hyundai will have it in an unnamed "rear-wheel drive premium sports sedan," meaning the Genesis concept car that debuted at the New York International Auto Show on April 4. The HD Radio consortium says at least nine automakers will have HD Radio by 2010, meaning six or more are still in the closet.

HD Radio provides a digital version of existing AM and FM stations, plus two additional channels of music, broadcast digitally on the same frequency. If the main signal craps out, the radio switches to digital. The other two channels have no analog backup, so in fringe areas, you're out of luck.

Jaguar plans to price HD Radio at the same breathtaking $500 price as BMW; add-on HD Radio adapters go for $200 (or less), as do many replacement radios. Hyundai hasn't yet set a price and won't for months to come, but it's expected to be lower. The question is whether Hyundai will be the first to swallow hard and make HD Radio standard. One auto executive whose company has worked with Ibiquity, which owns the technology behind HD Radio, said, "The next version of HD Radio is going to be called 'radio.'"