MIDIObjectSetIntegerProperty(myVirtualDestinationEndpoint, kMIDIPropertyAdvanceScheduleTimeMuSec, 1);
Which will make your app receive the midi packets ahead of time, so their timestamps will point to the future, and you can thus minimize latency. For example, scheduling a note-on in a synth app must be done ahead of time (due to audio buffer latency).. Or aligning an incoming midi clock phase exactly with your sequencer.
However, it seems to only work on virtual destinations. Meaning that you can get better timing by not connecting to other apps virtual sources, but instead let them send to your virtual destination. So this seems to be yet another reason why it would be best if we only ever used virtual destinations, and no virtual sources. :)
Cheers
/Jonatan