Steinberg is probably the only desktop DAW maker so far that takes iOS very seriously. Last month they released Cubasis, a DAW for iOS, which is a cut down version of Cubase. And now they release a Cubase iC Pro, an iPad controller app for Cubase. Steinberg says:
Connecting deeper to Cubase than any other app, Cubase iC Pro is your personal recording assistant. Up to four dedicated cue mixes can be set up, giving musicians the freedom to adjust their own mix with a phone or tablet. Cubase iC Pro is Cubase’s perfect companion!
Indeed, when you control both sides of the equation the deeper integration is easy. The app looks great, you can even see the overview of your multi-track session.