Star Trek? You know we have this technology at supermarkets now, right? :)
This still isn't truly a no-interface situation, though. It's an interface that's so natural that you don't have to think about it. You express your intent by walking toward the door. You're still expressing intent, though. The sensor just does a really good job interpreting that intent and acting on it. But like all interfaces, this one is still imperfect. e.g. Sometimes the door will open up when you're just walking too close. Or sometimes it doesn't open when you expect, presumably because it's poorly calibrated (or maybe you have no soul[1]).
If you observe carefully, Star Trek doors seem to detect intent rather than proximity. Sometimes people are just in front of them talking and as soon as they finish and want to get through, the door magically knows it needs to open.
On the other hand, when they are facing someone through the door and want to close it, they usually have to press a little button next to it.
Maybe it could be possible IRL with a face detector and looking at the direction and speed of the person.
But in many cases, you can eliminate the human-machine interaction itself. Machines can work in the backend, without you having to interact with them.
When I enter a shop and a ringer alerts the shopkeeper of my presence, I never had to interact with the machine at all - it just sensed me and acted in the background.
What you can strive for is interfaces that are so intuitive and easy to use that you don't need to fight them or rtfm.
Great UI designers know how to do this.