Well, it seems like IK Multimedia has beat Line 6 to it. Now you can leave the industrial strength cases behind in exchange for your iPhone and the iRig (of course you still need your guitar).
IK Multimedia has brought their renowned guitar and effects virtualization software to the iPhone with the iRig. For £29.99 you can purchase the iRig peripheral hardware that enables you to plug your guitar / bass into your iPhone and then your iPhone into your amp, sound desk -- whatever tickles your fancy.
The baseline iRig app is downloaded off the app store (which comprises of two stomp boxes, one amp+cabinet and two microphones). If you wish you can upgrade the app with more stomp boxes, amps+cabinets and microphones via the a-la-carte in-app purchase and download process.
We're very much looking forward to trying this out for ourselves. If the iRig plays like Amplitube does on the Mac, there are some exciting possibilities ahead, one of which being less back ache!
Check out the video after the break, or IK Multimedia's iRig website for more info.