Phocus (previously known as OWLE) sent over this case for me and I thought it would be a fun product to share since (especially as of late) I receive emails about various iPhone Video Rigs. The Phocus is a case for the iPhone 4/4s that allows you to add 1/4-20 accessories and a single hot shoe accessory. The iPhone needs to be removed from a phone case in order to slide in to the Phocus. The reason for this is to align the iPhone camera directly to the adapted lens for the sharpest results. It is a very snug fit which will also cause problems if you are using an iPhone screen protector.
Overall a great kit if you're a die hard iPhone Videographer. I have not found many other cases to fit such a niche that adds a hotshoe and tripod mounts to an iPhone, but a basic kit can run close to $100 dollars. The Phocus Kits are available in different bundles that come with a set of 2-3 lenses. Personally, I find the most useful lenses are the Macro for better close-up photography, and the wide angle lens for a wider field of view in video mode. The lenses are threaded so that you can attach optional filters and here i've found use for a Yongnuo Macro LED Ring Light. Information about the products can be found below.
Phocus iPhone Bundle 2 or 3 Lens Kits
iPhone/iPad/iPod touch Musical Instrument Microphone Adapter Straight Cable