Griffin's "ClearBoost" case for the iPhone builds in an external antenna tuned for AT&T's U.S. GSM/EDGE network, giving it an unfortunate tab at the top of the case, but bringing in "increased ability to maintain connection with the cellular network, with more stations available to your phone, and less interference from signal reflections." Interestingly, Griffin even has posted a video showing how to access the Field Test menu of your iPhone so that you can test the benefits of the ClearBoost on your own phone.
They're winging one over for review, so I'll brush my tooth and lotion my supple skin for you all soon and do a little review. I've not used a case with my iPhone at all—I find phone cases cramp my pocket—but my current iPhone's screen has a strange discolored area in the corner, so I'm hoping that Apple will cover that under the 1-year warranty. And if they do, I'll probably keep my new iPhone in a case, the better to sell it unscathed when the inevitable 3G version siphons a few hundred bucks out of my pocket. (And yes, I will make another donation to the EFF as a sin tax.)
An observation: If I didn't like my iPhone quite a bit, that strange LCD screen spot would probably be enough to cause me to think of the phone as "cheap" or "poorly made"; instead my enjoyment in using the device moves it into a sympathetic neutral zone, where I chalk up the discolored spot as an aberration typical to any mass market device. It's amazing how affection can color one's perspective—more amazing that Apple products seem to imbue solicitude. (Or charity's inverse, an involuntary psychic retch as the mind attempts to purge and protect itself from Apple's geas with antipathy.)
Oh, the ClearBoost costs $30.
Product Page [GriffinTechnology.com]