JamPlay.com is now offering an iPhone/iPad application available through the AppStore. Features include:

Video Lessons - Practice exercises or learn new licks and riffs while on the move.

Chord Library - Quick access to thousands of chords voicings.

Scale Library - Reference dozens of scales across all keys.

Backing Tracks - Jam to frequently-added backing tracks.

Metronome - Keep on time with the mobile metronome.

Tuner - Use your device's built in microphone to tune your guitar.