A free iphone guitar tuner. just incase you end up in the situation that you need to tune a guitar. im usually ok without, unless I have stressed ears, or im drunk. then it gets really frustrating. so if you ever find yourself in need:
http://itunes.apple.com/us/app/pitchperfect/id380781526?mt=8&uo=4
i found a free one on appstore
free optima guitar tuner
check out:
https://itunes.apple.com/us/app/pro-guitar-tuner-lite/id720274966?mt=8
You can try the online guitar here:
http://www.proguitartuner.com/guitar-tuner/
BR,
Johannes
cool :)