HD Radio isn't exactly Mr. Popular, but that can be attributed to the fact that people don't want to replace their car (where most radio listening takes place) radios. Directed Electronics' DMHD-1000 turns most factory or aftermarket radios into HD radios. One catch: it uses an FM modulator. Since part of HD Radio's draw is the higher quality digital signal, using the DMHD-1000 eliminates that benefit. You still receive all the HD Radio stations (we've got about 10 here in New York) but without the signal clarity that HD Radio usually delivers.
So now you have a decision to make: drop $200 on a device that will deliver only part of the HD Radio "experience," remain content with regular radio, or use what everyone else uses in the year 2007.
UPDATE: The Corporate Communications Manager just styled on me for slighting this radio. True, you can connect the DMHD-1000 using an FM modulator (which don't really have a sterling track record, at least not in large cities), but I neglected to mention that you can also connect it using a standard AUX port. Obviously, this will lead to a better experience all around. However, you're less likely to find an AUX port in manufacturer's radios than in aftermarket radios. So, new choice: use the less than optimal FM transmitter on your AUX-less radio or remove said manufacturer radio to install one with an AUX port. At that point, you might as well install a dedicated HD Radio tuner in your dashboard. I hope the communications man will accept a Facebook box of chocolates as an apology.