OK, so yes, this Leica i9 case for the iPhone 4 is still just a concept. You can't actually buy a case yet that fits around your iPhone and turns it into a Leica camera (though you can buy some nice lenses or an audio tape case). But this idea is just too cool to pass up. Outside of the standard retro charm of having a Leica attached to the back of your iPhone, the idea here is that you can use the iPhone's dock port to attach a high-quality premium camera to the back of your high-quality premium smartphone, enabling some really excellent mobile photography.
There's probably some technical magic that has to be worked here as well -- I don't know how feasible it is to have the dock hook up to and even control a high quality camera lens like this, especially with that design and size. But heck, if we can get the iCade made into a real product, this is certainly possible, right?