Saw this Open Source Bluetooth Keyboard and Gamepad for the Iphone. Looks pretty cool, it's up on Kickstarter. Ive backed it to use for my ipod touch but it will fit all iphones apparently
http://www.kickstarter.com/projects/1703567677/icontrolpad-2-the-open-source-controller?ref=live
http://www.kickstarter.com/projects/1703567677/icontrolpad-2-the-open-source-controller?ref=live