This is a simple sliding case style tripod mount for the iPhone 3G. All you need is one 1/4' by 20 nut that press-fits into the bottom of the case.
Insert a 1/4' x 20 (20 threads per inch) nut in the bottom. Epoxy or glue the nut in carefully avoiding getting glue on the threads. Slide the iPhone in, and mount on a tripod.