MIDI Pad is a new wireless MIDI controller app for the iPhone and iPod touch that’s inexpensive, but basic.
The intro video demonstrates how to use MIDI Pad (on iPhone/iPod) as a MIDI controller in Ableton Live
MIDI Pad provides one X-Y Pad, one slider and four buttons. It also translates your iPhone/iPod’s sensor signal (acceleration transducer and microphone) into MIDI signal.
MIDI Pad works using Apple Bonjour over WIFI network, so that you don’t need install any software or driver in your Mac to enable MIDI Pad. PCs are not explicitly supported.