Until recently, brainwave-reading devices have pretty much only existed in science fiction. Sure, electroencephalography (EEG), the technology that powers these devices, has been used in medicine and psychiatry since the late 1800s, but diagnosing people's brains and reading their minds are two totally different things. The first EEG headsets available to the public were used mostly ingaming and even in fashion, but in the last few years, they've gotten a little more sophisticated.