Haynes and his research team used a brain scanning technique called functional magnetic resonance imaging to detect a volunteer's unspoken decision to add or subtract two numbers flashed on a screen. They got it right 70 percent of the time. (from John's link)

They are somewhat better than chance (50 %) in deciding which one of two options the participant chooses when they know what the two options are and they have the participant keeping motionless in a scanner. No big deal so far.

Wolfgang