Now I'm thinking about it........it's not a problem solving device. It only takes care of a symptom. If your guitar goes out of tune alot, the problem lies in strings, bridge, vibrato, nut or tuners. If you have a guitar that stays in tune well, you won't need an auto tuner. If it doesn't, you can upgrade the guitar with all the thing mentioned above for a fraction of the price of that auto tuning gizmo.
One more thing. How long will the batteries last?
And I agree that mathematical tuning isn't always right.