An extraordinary video making the rounds today shows a monkey manipulating a robot arm simply by thinking. The question is, what’s the killer app? It’s not going to be about making robots move.

Experiments like this one involving both people and animals have been going on for years. The basic idea is simple: Electrodes worn on the head or embedded in the brain pick up brain waves and transmit them to a computer that interprets them in order to control a machine. Human subjects have proven able at using thoughts to control robot hands and move a cursor on a monitor, manipulate objects in virtual worlds, and even pilot boats.

Most popular articles on the subject (and there are lots) fall back on the obvious: thought-control of machines will be really helpful to disabled people. As the New York Times blandly put it: “Scientists expect that technology will eventually allow people with spinal cord injuries and other paralyzing conditions to gain more control over their lives.” This is surely right – paralyzed people are already test-driving the technology. But this will be a side-show for what will become the dominant application: connecting our minds directly with our avatars. This technology will make The Matrix real.

Already, experimenters have used mind control to animate an avatar in second life by simply thinking “walk” to make it walk . That’s just the beginning. It takes little imagination to see how this technology could allow you to make your avatar act according to your every thought, conscious or not -- smiling, winking, walking, talking, even crying, a perfect facsimile of your real-world self. You raise an eyebrow, so does your avatar. San Francisco-based Emotiv Systems has already demoed technology that gets part of the way there . Writing in The 2008 HBR List of Breakthrough Ideas, the MIT Media Lab’s Judith Donath explored the implications for virtual self-revelation – and deception – that such technology will permit. Couple this capability with the reverse flow of data – sights, sounds, touch -- from your avatar directly back to your brain, and you’re Keanu Reeves’ Neo following the white rabbit. Far fetched? Not really. Already, blind subjects have been given rudimentary vision through electrodes implanted in their brains. Deaf people have “hearing” provided by electrodes placed in their cochleas. The fundamental technology for pushing computerized sensory information into our brains exists.

This world may be decades off, but it’s inevitable -- and the business opportunities are mind boggling.