Check out this interesting comparison of consumer brain-computer interfaces on Wikipedia.

Emotiv is apparently coming out with their EPOC in Q4 2009. The page says:

Due to the complex detection algorithms involved, there is a slight lag in detecting thoughts, making them more suitable for use in games like Harry Potter than FPS games.

Obviously faster computers would help here. People ask about the economic motivations for why the average person would want faster computers. This could become one of them.