I tested a very similar device for the company I used to work at, the UI looked identical at least. There was very little relationship between my actual mental state, and the state of the display. The device I used had an API, so I wrote my own visualizer to make sure they weren't just blurring out the data -- long story short, I was never impressed with it. Blinking or moving your head triggered a larger reaction than any thought impulse.
Maybe the tech has gotten better, but I wouldn't hold your breath for anything that costs $100.