We’ve also seen lots of physical additions to the iPhone camera. You can get wide-angle lenses, telephotos, and even a 12 xmicroscope lens. But a team of researchers at UC Davis has one-upped the competition by making the iPhone into a 350x microscope for very little money.
The original PLoS One paper is here. I am longing for an integration of something like ImageJ in the iPhone. You would end up with a terrific tool.