Apogee Jam Guitar Input - Apple Store (U.S.)
Damn, this looks cool. An actual dock connector for the devices, instead of the 1/8" adapter idea. For $90, it's twice as much as the iRig and Ampkit, however I think it may be worth it, given that it's Apogee, and it uses the dock connector.
Also has a USB connector, so it'll work with a Mac too, for GarageBand, and presumably NI4, Amplitube, etc.