What DARPA wants to develop — at least in the short term —  is a tool for students who want to know how to read the basic states of a classmate's mind. But EEG readings as a form of lie-detection are already in development and DARPA does admit to wanting to send EEG headsets out with troops as part of a medic kit.

Once created, cheap and mass-produced EEG reading headsets could have an array of uses, especially when their data can be read with any smartphone. There's even the chance that they'll eventually be able to read your thoughts. For now however, that's all still stuck staunchly in the future, as the deciphering of detailed data from an EEG reading is simply beyond the reach of modern understanding of the complex math involved.