I saw this link to a simple mod to add a cheap 45X microscope on the the I4 for $5. just figured I pass it along I just ordered mine yesterday. I also ordered a cheap Mini 8X21 Monocular Telescope to try for fun.
iPhone as digital microscope
http://www.tuaw.com/2010/09/06/cool-mod-iphone-as-digital-microscope/
iPhone as digital microscope
http://www.tuaw.com/2010/09/06/cool-mod-iphone-as-digital-microscope/