I already support virtual MIDI ports. If a virtual MIDI port has been created on the device, you go to Settings->MIDI Settings->Configure MIDI Connections, change the library to Google and uncheck the checkbox at the bottom left, any virtual MIDI ports will show up as something you can connect to. I've tested this in the past with other apps such as the Soundbrenner metronome app. The only thing I don't currently support is rtpMIDI which I can't give a timeline for supporting yet.
Mike
Mike