shapeways:

3D Printing an iPhone 4 Macro Lens
 

Make your own slide-on macro lens for the iPhone 4 or 4S with $11 worth of 3D printing and a $4 lens from the Surplus Shed.  This is an interesting use of 3D printing to help extend the  capabilities of an existing product.  Quite an amazing level of detail  is achieved with just a few inexpensive parts, see the image below of  the ruler taken with the slide-on macro lens.

shapeways:

3D Printing an iPhone 4 Macro Lens