Pro Guitar Tuner for iOS - FREE

[ctgolfer]

‎Pro Guitar Tuner

‎The guitar tuner app used by professional guitar makers, guitar repair shops and musicians around the world. The app listen and analyze the sound in real time from the built-in mic, headset, guitar clip on or from any other external microphone. It is so accurate that it will be your best friend...

[pitcherswife]

thx @ctgolfer still valid