This has been a headache for me for years -- and I haven't settled on a solution.
Obviously, if you have a MIDI foot-controller with a built-in expression pedal (e.g. Behringer FCB1010) or to which a foot-controller can be attached (e.g. IKM's Blueboard), that's one way. But I use Amplitube principally for home-recording, and I'm not particularly interested in doing anything else with a foot-controller (other than using the expression pedal to control Amplitube's wahs, etc.). So those would be expensive solutions that leave me with big blocks of unwanted hardware.
Now there are some MIDI-pedal-to-USB adapters on the market, e.g. Audiofront's "MIDI Expression". In theory, I presume one plugs the expression pedal into the adapter, and the adapter into the computer. I don't know if anyone has tried this with Amplitube, and I'm a little leary about investing in the hardware in case it doesn't work. I'm in S. America, so gear is scarce and expensive locally, and I would probably have to wait until I was in the US to get these things, and then bring them back to try out. So far, I've just considered it to be too risky an experiment.
All that said, I'm very intrigued by the forthcoming iRig Stomp I/O, which looks like the IKM-native successor to both the Stealthpedal and the never-actually-marketed Stealthboard. It's got an integrated expression pedal and is a proper USB audio-interface as well -- with even phantom power for attaching a condenser mic. I expect my current audio-interface (a 2i2) to last me some time, but the iRig Stomp I/O would be a tempting future solution. I'm actually already hoping for a "version 2"
![Cool 8-)](./images/smilies/icon_cool.gif)
that has 2 audio inputs, so I could have an instrument and a mic running through it simultaneously. That would basically solve all my audio/MIDI interface problems.
![Mr. Green :mrgreen:](./images/smilies/icon_mrgreen.gif)
So if a new audio interface is also attractive, you could hold out for iRig Stomp I/O to hit the market. Otherwise, you could try running the FC7 into a Blueboard, or a MIDI pedal adapter or something. The main thing is that I don't think you can attach the FC7 directly to your computer (or mobile device); it has a 1/4" cable that has to go into some MIDI unit that, in turn, can talk to your computer (or mobile device) via USB.