All you do is hold the String Master robotic guitar tuner on each tuning peg and pluck the string. String Master listens to the sound and its powerful gear motor actually turns the peg for you until that string is tuned to perfect pitch.
Nice idea, especially if you're in a hurry. Probably just a matter of time 'til a company like Line6 starts building them into guitars, since they've already put a ton of other electronic doo-dads in their axes.
BigAssSuperstar got stuck a few months ago with a mistuned guitar. I went up on stage for a quick song, and in my rush to get set up, told my PodXT that "A" was not 440Hz, and proceeded to tune a string to that wrong information. Panicked, all I could do in a hurry was tune the rest of the guitar to the mistuned string by ear, as the audience looked on. Doh. I think I'd look just as foolish bringing something like a mechanized ratchet on stage to auto-tune the thing for me.