This Guitar trainer for the iPad from Ion Audio runs $100 and is basically a guitar shaped tablet accessory designed to teach you to play the guitar. As a person that already tried once (for 6 months) to learn to play the guitar, I think this may be a nice alternative to trying to figure it out on your own!
Guitar Apprentice is a full-scale, electric-guitar-style controller that transforms iPad into an amazing guitar-learning experience. Simply place your iPad into it's fitted holder, open the Guitar Apprentice app, and you're ready to go. It can be played anywhere as it requires no cables or external connections. It's strings can be strummed together or plucked individually, and its 14 fretboard-fret buttons mean you can easily play thousands of songs. This is similar to the iTar Guitar that came out a few months back.