Well, sort of.
A company called iPhoneDSLR claims that you can do exactly as the claim with their product, an SLR lens mount for iPhones.
The”iPhone DSLR prototype” is a 1.1lb, solid piece of anodized billet aluminum that will fit an iPhone 3G, 3GS or 4 and a full-size Canon EF lens.
Does this turn your iPhone to an actual SLR? The answer is no (except maybe for the looks). Will it let you take better pictures? Maybe. But that’s only because the company has yet to provide any sample output from their product.
source Slash Gear, iPhoneDSLR