Virtual Reality headsets are used to give gamers the experience of a virtual word using video and sound. Now three different companies are coming out with an add-on that adds scent to the VR experience. This is light years beyond the failed Smell-O-Vision technology of the 20th Century. WBGO's Jon Kalish reports on a Vermont start-up whose device will soon be used by psychologists treating veterans with PTSD. Click above to hear Jon's feature on OVR.