A first person account from CNN.com:
A special headset was placed on my cranium by my hosts during a recent demonstration at an NTT research center. It sent a very low voltage electric current from the back of my ears through my head -- either from left to right or right to left, depending on which way the joystick on a remote-control was moved.
I found the experience unnerving and exhausting: I sought to step straight ahead but kept careening from side to side. Those alternating currents literally threw me off.
The technology is called galvanic vestibular stimulation -- essentially, electricity messes with the delicate nerves inside the ear that help maintain balance.
I felt a mysterious, irresistible urge to start walking to the right whenever the researcher turned the switch to the right. I was convinced -- mistakenly -- that this was the only way to maintain my balance.
The phenomenon is painless but dramatic. Your feet start to move before you know it. I could even remote-control myself by taking the switch into my own hands.
The rest of the article.
Apparently, the technology has applications ranging from video games, to music, to non-lethal weaponry. But, more likely than not, people will just use it to screw with each other when they're drunk.