The vicon plug-in works with a protocol used by earlier versions of Tracker. You should be able to use vrpn to read body data from tracker in Vizard once you specify the correct VRPN source.
Code:
import viz
import vizact
import vizshape
viz.go()
VRPN_SOURCE = 'Tracker0@localhost'
viz.move([0,-1,-5])
axes = vizshape.addAxes(length=0.5)
vrpn = viz.add('vrpn7.dle')
headtracker = vrpn.addTracker(VRPN_SOURCE)
headtracker.swapPos([-1,3,-2])
viz.link(headtracker,axes)
def showData():
print headtracker.getPosition()
print headtracker.getEuler()
vizact.ontimer(1,showData)