Turn an iPhone into a universal remote with UIRemote, which plugs into the audio mini-jack.
iWatch. Wrist watch band for the 6th generation iPod Nano. If I had this a decade ago, I probably would have cheated on tests in school more.
Heat sensitive iPhone 4 back from RF Laserworks. $12. Click for video.
"Megaphone" for iPhone. A large ceramic horn amplifier. Click to watch a Vimeo video.
iPhone SLR mount ≈ $250.
Visual iPhone charging dock displays charge with LED's. Not a lot of information out there on where to acquire this product. It may well be only in conceptual stages.
XDModo sleek solar iPhone charger. $64.
DIY iPhone microscope. A 45x zoom scope costs only $5 to make.
Solar Window Charger
Macro, telephoto and fisheye lenses for iPhone 4. A magnetic ring locks them into place. $50 for all three.