I got to share this with you all - scientists have succeeded in communicating with lucid dreamers in a sleep lab. This is beyond eye tracking to signal you are lucid. This is actually someone awake realtime communicating with someone who is lucid dreaming.
Maybe even get real shared dreaming powered by technology at some point. If you manage to align the sleeping cycles and have elaborate methods of communicating in and out of dreams, it will even possible to synchronize them across sleepers to some degree. How awesome would that be?