this is an old post.. is it now possible to do this??
Yes, in a sense. In H9 Control you can select a MIDI port and send it's messages to the H9 over Bluetooth (this is under Settings).
Some people asked us to have H9 Control create its own virtual MIDI port that could be opened in another app and written to from another app, but we couldn't get this to work well, because it caused other unexpected problems with the Bluetooth connectivity. So, we don't support this.