The iOS accessory company 60beat has released a new gaming controller for the iPhone, iPad and iPod touch. The $50 GamePad allows you to use a physical controller instead of the annoying onscreen controls of iOS games. Unfortunately it only works with two titles (Bugdom 2 and Aftermath) right now, but I assume there will be more GamePad compatible games in the future.
The GamePad is a great accessory if you enjoy playing games on your iPad at home, but I doubt anyone is going to want to lug this thing around. It resembles a PS3 controller with dual analog joysticks and 8 action buttons. There is no Bluetooth wireless option. The GamePad connects to your headphone jack with a 4 foot long cable. That's a lot to take on the bus, but maybe not such a bad idea for kids on long car rides. Especially since it doesn't require any batteries.