We have seen one of these cases before from Factron which adds a lens to the camera of your iPhone, the Factron iPhone Case and Fisheye Lens, now there is a new version available that will add a total of five different lenses to your iPhone camera, the Factron Simplex iPhone Case.
The Factron Simplex iPhone Case will fit both the iPhone 3G and iPhone 3GS and it comes with an attachment that lets you add various lenses to your iPhone case for different effects.
The lenses can be purchased as well as the case and the ones available include a 40mm macro lens, a 25mm macro lens, a super wide angle lense, and two Fisheye lenses.
The case is available for about $196 and each lens costs between $19 and $60, which means it could work out quite expensive if you want all five lenses.
Factron via Le Journal Du Geek