If you're able to get the Nexus data into Vizard, you should be able to apply that data to vizconnect trackers and use optical heading. First add two group trackers from the trackers tab. Then apply the group trackers to the optical heading tracker. In the postInit() function of the vizconnect file set their raw trackers to be the Nexus trackers:
Code:
# update nodes with nexus data every frame, here they are called nexusLeft and nexusRight
# get handles to group trackers added through trackers tab and apply
# nexus data to them
vizconnect.getTracker('nexus_left').setRaw(nexusLeft)
vizconnect.getTracker('nexus_right').setRaw(nexusRight)