ofxCoreMIDI is the beginnings of an example project that allows the PGMidi class written for Objective C to be used with relative ease with OpenFrameworks. Currently the example only caters for MIDI-out but it's a start!
This example project has been tested in openFrameworks 0062 iPhone build.
Download the example project and place it in your /apps directory. As well as openFrameworks, you will need to add the Source directory from PGMidi to your /src directory so that it looks like /src/Source. You can download that from here.