Last night's 'Re-inventing the Body' episode of The New Inventors took a look at the fascinating Epoc Headset. Essentially it identifies the type of thing you're likely to be thinking about (based on the amount of electricity being produced by various parts of the brain), and translates it into a virtual action.
Many, many uses; though initially it will be used as a gaming control (gamers may have already seen an early version at the last GDC). Personally, I'm looking forward to see the plethora of Wii Fit-type games which will undoubtedly appear.
How long do you have to wait? It should be out later this year.