USB Fever has released the 6X Telescope with Crystal Case for iPhone 4G
(http://www.usbfever.com/index_eproduct_view.php?products_id=2020), an US$18.99 case with an expansion telescope.

If you don’t want to be bounded by the built-in camera on the iPhone, now you have a way to “expand” its functions. This telescope has a 6x expansion that can help you to shoot close up on objects.