But our world is becoming more and more like a Doglas Adams novel - I seem to remember in one of the H2G2 books that they considered their civilisation so advanced that they did away with TV remotes, and the TV could detect that you wanted to change channel when you make a gesture. The upshot being that if you didn't want the channel to change or the volume to suddenly shoot up, you had to sit completely rigidly still for the duration of your programme.