From Mauvila Software:
A versatile chromatic tuner for a variety of instruments. A real, microphone-based guitar tuner and much much more.FEATURES:-A sophisticated pitch detection engine that works with most musical instruments, including stringed instruments, woodwinds, and brass-A fretboard mode that helps you tune stringed instruments, including banjo, mandolin, ukulele, bass guitar, and many more.-Works great with the standard guitar tuning as well, and has a dedicated module for this.-A standard note display that accurately reports both the note name and the octave of the note played-A display that reports the frequency of the note played-Multiple guitar tunings-Easy-to-use hands-free interface-Optional non-standard note frequencies (via changing A4)-Both LED and analog pitch metersCompatibility:iPhone (4S and later): compatibleOther iOS devices which have microphonesNote: some users have reported that the microphone is not working in the latest release immediately after updating the app (especially users of iOS 9). If this is the case, reboot your phone (holding power & sleep button down for 20 or so seconds). The software should work as expected thereafter. If this does not resolve your problem, contact support (email@example.com) with your OmniTuner version as well as the type of device and your iOS version.
-Ability to turn off auto-sleep mode on the iPhone-New standard guitar tuning module (akin to TyroTuner)-fixed bug in some devices where microphone would quit working after resuming previously started app-fixed bug where app would lock up on deleting a custom tuning