I just was in a radioshack and saw that they had a dongle for the iPod that says it allows iPod and iPhones to receive FM radio and HD radio signals. It was in an area with a bunch of clearance items and the price tag was only $9 so I decided to pick one up. I had wanted to get an HD radio receiver however I never did because they were all over $100 and even now they are still over $50. I'm happy to say that the device also works perfectly with the iPad. I tested it on my third generation iPad.
There is a downside however, I already use my iPad to play music or audio streams in my car and I do it all over bluetooth to my car stereo. I had hoped to listen to HD radio from my iPad via bluetooth to my car stereo but the device/app does not support this. It seems that the dongle is being powered by the iPad 30pin connector and all audio is sent out of its own audio headphone jack. The device communicates with the iPad allowing you to select channels, display current song info etc... but its not sending the audio to the iPad itself.
That being said I think that the HD Radio dongle is still worth the $9 I paid for it and I plan on taking it with my on my trip out of town this month.
The dongle is made by Gigaware, and the sku number is 040293584559