Saw this Roadie Tuner thing on a Facebook ad. It is essentially a battery operated string winder you can pair up via bluetooth with your smartphone. You can download an app, and this thing uses your phone microphone and string winder to automatically tune your guitar. Has anyone tried one of these? You just pluck the string you want to tune and it tightens/loosens string until the string is in pitch. You can do alternate tunings with it also. I'm thinking about getting one.