This sample shows the basics of how to probe for the MIDI hardware and endpoints available on the system as well as sending a simple note to all of the MIDI devices connected to the system.
For more information about CoreMidi in MonoTouch, check the online API documentation that includes an explanation of the different pieces:
http://iosapi.xamarin.com/?link=N%3aMonoTouch.CoreMidi
Miguel de Icaza ([email protected])