Photos: Scanning brain waves

Hans Lee, chief technology officer of EmSense, wearing the company's wireless headband, which includes a dry EEG (electroencephalogram) sensor to measure the electrical activity of the brain without the use of gels; an accelerometer, which detects motions and facial twitches; and a heart-rate monitor that can gauge stress rates.

With data from these sensors, EmSense can detect whether or when the wearer blinks, blushes or sweats. Advertisers and video game companies are using the technology to find out how people feel about their products and sales pitches.