In a world of gimmicky peripherals, the GameBone Pro doesn't do much to help its case — on the surface, that is. Yet it's got a couple of nifty features that make it less ridiculous then, say, a USB microwave.
The coolest thing the GameBone will do for you is give your iPhone a bit of charge while you're playing it. The downside? You have to have it plugged in to the iPhone 30-pin port. The GameBone can also be used via Bluetooth, though obviously you can't charge the iPhone wirelessly.
So, if you're dying for a D-pad and some buttons, maybe the GameBone is what you're looking for. That said, it doesn't have any way to hold up the iPhone, so you'd have to prop it up, or hope that 22Moo, its Australian manufacturer, makes good on its plan to ship it with a stand. (That said, you're really ditching the beauty of portable gaming at that point.)
22Moo wants to ship the GameBone Pro sometime in September. As for the price, they're looking for visitors to their website to tell them what sounds good.