Want a guaranteed, sure-fire way to enrage DSLR enthusiasts? Call your custom-crafted iPhone 4 mount that allows you to use interchangeable lenses an "iPhone DSLR prototype"; you'll soon have them queueing up to point you at the official definition of a single-lens reflex camera. Still, we'll put aside nomenclature because there's something sturdily lovely about Jeremy Salvador's system, no matter what he wants to call it.
The chassis is a 1.1lb solid piece of anodized billet aluminum with dual handle-grips and a tripod mount; up front is a Canon EF lens adapter, which Jeremy hopes to extend to support SLR lenses from other manufacturers. It'll actually work with the iPhone 4, iPhone 3GS and iPhone 3G, though of course the latter two don't pack as many megapixels or the iMovie app for on-the-fly video editing.
There are still questions - when they're not berating him for his choice of name, commenters are asking about the difference in image circle between what size sensor an SLR lens is designed to work with and the sensor in the iPhone 4 - and Jeremy is yet to show any sample shots from the rig, but as we saw with similar systems for earlier iPhones, people just seem to love to make complicated mounts for relatively mainstream cameraphones.