|Camera hacker Bhautik Joshi has built an optical adapter - the Phone-O-Scope, so he could attach SLR lenses to the iPhone. [ link ]
"Just to get the inevitable question of 'why' out of the way - well, why not? As far as I can tell, I think this is the first - I couldn't find any similar SLR lens to camera phone attaching attempts anywhere else online. The Phone-O-Scope doesn't take especially superb images, and it's a bit clumsy to handle. On the other hand, it's fun to shoot with and produces very analog (almost Holga-like) results. You also get the advantages of SLR lenses - that is, DOF effects, and the wide range of available focal lengths (i.e. macro to telephoto). "