I've used a few different setups to use my iPad as a midi controller for Modul8. I ran into this app a while back and it's been the best one I've used so far. Midi Designer Pro lets you make your own midi interface and connects to the computer via wifi or you can hard wire using the iRig or the iConnect. Unlimited buttons,knobs,sliders at your disposal is a pleasure and the app is constantly updated with new features. It's worth taking a look for those who want to use their iPad as a controller.
http://mididesigner.com/
https://itunes.apple.com/app/midi-desig ... n-mpt=uo=4
http://iconnectivity.com/