ThinkGeek offers the Ion Audio Icade Mobile Game Controller for iPhone / iPod in Black, model no. ICG07, for $24.99 plus $6.04 for shipping. That's the lowest total price we could find by $19. It fits the iPhone 3G, 3GS, 4, and 4S, as well as the 2nd-generation iPod touch. It turns your iPhone or iPod touch into a controller and features Bluetooth, buttons, D-pad, rotating cradle, and more. It operates on two AA batteries (included).