The Mobile In Audio Interface for iPhone 4, iPad & iPad 2 from Line 6 allows you to connect a guitar to your iPhone or iPad to turn your device into a pro modeling amp -- and get a range of amplifiers, guitar cabinets, stompboxes, tones and rack effects. In addition to the physical interface, a free mobile Pod app can be downloaded for full functionality.
The adapter connects to the 30-pin digital input on the bottom of your device rather than the headphone connector for superior audio signals, and supports up to 24-bit/48kHz digital audio. You'll get an impressive 110 dB of dynamic range and 98 dB when you use another mono or stereo line level. Additionally, the device records and works with other CoreAudio apps like GarageBand. A high-quality guitar cable is included for convenience purposes.