Guitar Toolkit app
GuitarToolkit is a collection of essential guitar tools for your iPhone, iPad and iPod touch. It has a tuner, metronome, more than two million chords, scales and arpeggios.
It also provides support for a multitude of instruments, including ukulele, banjo, mandolin, and all kinds of bass and guitar. It comes recommended by CMST guitar teachers.
Find out more here: http://agilepartners.com/apps/guitartoolkit/