I must admit to being a little unsure about this one... it's The Performer from TransPerformance. This fairly large and complicated piece of machinery will keep your guitar in tune, in any one of a number of different tunings. The tuning can happen almost instantly, though you have to strum on open strings to do it. You can preset the device to store as many as 240 tunings. When a tuning is selected, sensors and motors adjusts the tension on all six strings simultaneously. In addition to the fairly substantial piece of hardware at the bridge, there's an LCD screen cut into the side of the body that shows the note, octave and cent value of all six strings.
And I thought the Robotic Tuner was pretty whacky!
At the moment it's available for hard body guitars (Les Paul's and Strats) but there's probably no reason it couldn't be adapted for acoustics; other than it's large and heavy! on second thoughts, looking at the size of the bridge, maybe not in it's current configuration.
CNET has an article about the device. I'm not sure of the price; and not sure I want to know.