Binaural Beats are weird. Discovered in 1839 by Heinrich Wilhelm Dove, a German physicist and meteorologist, they're auditory processing artifacts created when you play sounds of slightly different frequencies to each ear. A beating tone is percieved, as if the tones mixed outside the brain. The weird bit, however, is that they appear to entrain brainwaves, producing relaxation and health benefits. Enter the FeelFree headset.
It's a concept product, produced by Nike, which sits on your head and uses bone conduction to play the binaural beats to you without affecting your hearing. Waves above 40Hz will help you solve problems and increase perception. Waves between 13 and 40Hz help you concentrate or become aroused. Waves between 7 and 13Hz will help you relax or become drowsy. Waves from 4-7Hz are associated with dreams and REM sleep, and waves below 4Hz are associated with deep, dreamless sleep.
The process works best if you start near a person's currently dominant frequency and slowly reduce it to the desired level, so the headset also includes devices for measuring the frequency of your brainwaves. The headset comes with four modes - meditation, focus, learn and sleep, which roughly correspond with the frequencies listed above.
The technology's around for this product to be created tomorrow - it's just a case of miniturizing it enough to fit into a small, light headset. Do binaural beats work? Well, your milage may vary. The Wikipedia article about binaural beats is riddled with s, and there's a few references to lucid dreaming and out-of-body-experiences.
If you're into that sort of stuff, then you might find binaural beats interesting, and there's some sample files on Wikipedia that you can feed into your headphones to try it out. I'm playing them now, however, and not feeling especially more relaxed than I was half an hour ago. I am sleepy, but I think that's more of a relic of playing Civilization IV all night than anything to do with brainwaves.
As it's a concept product, there's no release date or price attached. The concept does have some scientific basis, but I remain to be convinced of its large scale effectiveness.