From MSNBC.COM:

Mind-reading toys could revolutionize play

Technology could make games more mentally stimulating and realistic

SAN JOSE - A convincing twin of Darth Vader stalks the beige cubicles of a Silicon Valley office, complete with ominous black mask, cape and light saber.

But this is no chintzy Halloween costume. It’s a prototype, years in the making, of a toy that incorporates brain wave-reading technology.

Behind the mask is a sensor that touches the user’s forehead and reads the brain’s electrical signals, then sends them to a wireless receiver inside the saber, which lights up when the user is concentrating. The player maintains focus by channeling thoughts on any fixed mental image, or thinking specifically about keeping the light sword on. When the mind wanders, the wand goes dark.

(more here)