A little while ago, I signed up to participate in a research study in which some neuroscientists and engineers were designing systems to predict visual tracking based on cortical activity in the brain. The basic research was meant to increase understanding of neurological physiology. Potential applications included (top secret) use by the military and tools that quadriplegics could use to control motion.
The protocol involved me lying in an MRI machine while an image was displayed in a visor. I alternatively controlled a cursor or just tracked it with my eyes. The MRI then measured oxygen use in my brain. I am guessing that some end product would use electrodes instead of MRI given MRI's bulk (>4 tons) and expense ($Millions)!
Anyway, for an hour of my time, I pocketed $25 and this nifty 3D view of my brain.