This is the professional version of DaTuner Chromatic Tuner, reviewed recently on Android Central:

"For the Android-loving musician, I think DaTuner Pro is easily the best tuner you can have on your device. I used to give that title to *see review!*, but DaTuner has proven to be so powerful, easy to use, and accurate, it'd be foolish to not use it."

http://www.androidcentral.com/android-app-review-tuner-datuner-pro

DaTuner is an all-purpose chromatic tuner with a simple interface. DaTuner converts the fundamental frequency to the nearest note and error in cents for quick and easy tuning of your guitar, ukelele, violin, bass, cello, mandolin, piano, harp, saxophone, balafone, Ducati timing belt, harmonica, kazoo, you name it.

1.) No dead zone - screen changes to green when tuning is good.
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