I was watching the very first Star Trek pilot, and I noticed that for one brief second Spock seems to use a spatial UI gesture to control the big screen.
If you have streaming Netflix, you can see for yourself right now. Perhaps you can check whether I'm mistaken. The episode is called "The Cage", and the moment I'm talking about is at 2:29. It looks like Spock swipes his finger in the air from left to right, causing the screen to change from a view of space to a map of some planets. He then says "Records show the Talos group has never been explored."
I learned from Wikipedia that although this episode was completed in 1965, it wasn't broadcast until 1988. Even with the 23-year delay, I wonder if it was the first example on TV of a spatial gesture-based UI, long predating "Minority Report" and the Kinect. Maybe not; I haven't watched all that much science fiction.
I'd like to see someone try to use this as a prior art argument in a patent lawsuit, as was done with the tablets in "2001: A Space Odyssey".