GuitarJack Model 2 is the perfect companion for GuitarTone ($2.99), Taylor EQ (available in FourTrack), FourTrack and StudioTrack. Enables $19.98 worth of GuitarTone amps and effects. Works with most 3rd party apps like GarageBand.
Engadget.com - "GuitarJack Model 2 is a handsome, well-built adapter for capturing ideas in instrumental and vocal form. Machined aluminum housing looks nice...alleviated fears about damaging in a gear bag."