From Matthew Finn:
Cleartune is a chromatic instrument tuner and pitch pipe that allows you to quickly and accurately tune your instrument using the built-in mic in your iPhone or using an external mic on your 2nd or 3rd generation iPod Touch. Cleartune features a unique "note wheel" interface allowing you to quickly find your pitch, paired with a highly responsive fine-tuning meter for the perfect tune. With support for custom temperaments, transposition, notations such as solfege, adjustable calibration and more, Cleartune packs more power than most pro tuners, yet is simple enough for everyone to use. Cleartune can tune acoustic or electric guitar, bass, bowed strings, woodwinds, brass, piano, tympani, tablas and any other instrument that can sustain a tone. Most electronic tuners cannot properly tune a violin. With a built in temperament for violin family instruments, Cleartune will have the 5ths singing perfectly.