I bought 3 twin-packs of D'addario XL's, and they came with these little pick shaped tuners. They looked like a joke to me, but I tried one and it actually works and works great! You turn the dial to the note you want to tune to, pick the note, and hold the lights inside it on the 12th fret. The lights will strobe until you get in tune. Sounds cheesy, I know, but it tunes. It only tunes to fixed pitches B, E, A, D, G, C, so if you tune down you're on your own for an F, but it'll tune a 6 string to standard tuning, and it works on guitars, too. I was actually impressed. It's a good little quick and dirty tuner. A bit too fussy to use onstage, but great for the hotel room.