
It's called
Guitar Toolkit, and it's an application you can install on an iPhone (or a second-generation iPod Touch). Fact is, I always have my iPhone with me, and this application takes the place of a bunch of other stuff that I used to have to pack around.
What is Guitar Toolkit? Well... put it on your iPhone and you have: a tuner (for standard and dozens of altered tunings), a notated fretboard (showing notes and note positions for all tunings), a metronome, a chord finder, and ... all of this for a 6-string, 12-string, and bass guitar.
This is a seriously cool application, and will change the way you think about your guitar.
I mean it. Suddenly: it's easy to find a chord, a variation of a chord, tune your guitar, practice difficult runs with a metronome... and all of this: with the iPhone that's already in my pocket.
Ever spend a relaxed afternoon, learning new music with keyboard (or other) players, when they call you out and say "wait, stop... that should be a C#M7sus!" Which is... what? Like I had memorized those finger positions for a chord I've never heard or played? Yep: Guitar Toolkit will show you that goofy chord with the flick of a finger.
I used to have a 'Favorite Tuner' and chord charts and etc that I would move among the cases for my guitars. Which meant I would sometimes get somewhere, missing the tuner that was packed with another guitar. This Guitar Toolkit solves all of that and so much more, and YES you need one.