EmSense's San Francisco office

A view inside EmSense's San Francisco office, where it employs neuroscience researchers, mechanical and software engineers, and marketing types. It employs a total of 21 people in Monterey, San Francisco and Santa Monica, Calif., where it hopes to build stronger ties with Hollywood.

The company has largely operated in stealth mode since its founding in 2004, and it remains covert on many subjects, including how its backend technology works. EmSense has only one publicly disclosed customer--THQ--but Lee says the company has had deals with several advertising clients since January. Similarly, Lee would not disclose how much the system costs potential customers.