The iPad/iPhone platform keeps getting more and more interesting. This new app, MIDI Surface from Audiofile Engineering/Line 6, turns your phone/pad into a midi controller when hooked up to Line 6's MIDI Mobilizer (a hardware midi interface for iPad/iPhone, required).

MIDI Surface is a full-featured MIDI control surface built exclusively for iPhone and iPod touch, brought to you by the minds at Audiofile Engineering. Combining powerful, elegant and uncluttered audio utilities with unparalleled technical support, Audiofile Engineering is one of the most innovative and experienced audio software developers for Mac OS X, iPhone and iPad.

Control Surfaces:

Keyboard: (Channel, Velocity)

Sliders: (Channel, Controller (Mod Wheel, Channel Volume, Expression, etc.), Low Value, High Value

Drum Pads: Channel, Category (Note On, Controller, Program Change), Note, Note Off (Immediate, Touch Up), Velocity

X-Y Control: Supports up to 4 touches, Channel, Controller, Left Value, Right Value

Each interface can be configured with great detail and you can save Presets for quick recall.

Check out and buy ($5.99) MIDI surface here

And check out the MIDI Mobilizer interface here