I've seen it before. The audience is given a hand control in which they puch a button up or down as it relates to their current opinion of what is being said. I don't think it's anywhere near a standard lie detector test.

it's used in marketing and advertising and campaign management to gauge consumer response to media. The had a guest on NPR once who was the creator of this process and a very successful political ad consultant. He did a lot of research in terms of elements and types of advertising (positive, verses negative political ads) and how it affected viewer opinion.

Basically it's an updated version of the applause-o-meter

Its called the "Instant Response" focus group technique pioneered by Dr. Frank Luntz.  They can pinpoint exactly what people like and dislike by their words.  The higher the meter the more they approve of what you are saying, and the lower the meter the less they approve of what you are saying. 
This way you can adjust your wording to your audience and have mass appeal.  Marketing is great.

rs