There was a guy at MIT about ten years ago (edit: 2018! Woah) who made a headset that would read electrical impulses from your face. Apparently when people think in words, the same nerves fire as when they speak, just at a lower activation level. Using those signals it is possible to reconstruct the words being thought.
I'm surprised it didn't seem to go anywhere.
Edit: found it https://youtu.be/RuUSc53Xpeg