For those using the Lie Detector app which is part of Denis Behr's trick in Seventeen Secrets Volume 2, he made a small update which improves the working. You should go to his site and redownload the app to get the slightly better version. The method behind the trick remains exactly the same, but the output of the app has been made slightly clearer, which makes the effect clearer in the eyes of the audience. The change came about because of suggestions from Dani DaOrtiz while he was in Toronto recently.
For those of you that bought the book but haven't tried the trick because of the [secret stuff] involved, you should. It's one of the most ingenious combination of diverse principles that I have ever come across and the result is an iPhone that appears as though it can read minds.