This video offers a review and demo of IK Multimedia’s iRig and Amplitube.
The iRig cable is an adapter that allows you to connect you guitar to your iOS device like an iPhone, iPod touch, or iPad. The iRig from IKMultimedia.com retails for $40.
IK Multimedia offers two apps that work with the iRig. One is the free version and the other is the full paid version for $19.99.