Retro Tuner

Retro Tuner is a musical instrument tuner for the iPhone, iPad, and iPod Touch. It features a user interface in the style of an analog panel meter and Nixie tube note display, but below this retro surface are all-new digital signal processing algorithms that determine the pitch of your instrument quickly and accurately.
Retro Tuner was written by the owner of several crappy guitars and a 1920s player piano that is constantly going out of tune, with the idea that if it can tune those, it can tune anything.
Retro Tuner tunes in equal temperament and can handle the full 88-key piano range. The reference pitch defaults to A=440 Hz and can be adjusted via Settings either as a frequency in Hz or as a detune factor in cents.