Null zone assessment

In this video, http://www.youtube.com/watch?v=3Czylz0yhu8, from minute 1:21, you can see a woman undergoing a null zone assessment (does she wear her panties?). Do you know anything about this procedure?

I read that involves the placement of a thermometer in the rectum

Yes, the temperature is measured in the rectum. It is also measured in the esophagus.