At first I was excited about this. I practiced with the helpful tests at the end. (however they
should have given more trials and more than two people as this is hard to learn without live
practice and the video is a great way to sub that. However I went to describe this great thing I
was learning to a female friend and she said "Aren't you just able to.." and she had the method
without ever seeing it.
So this one got pushed aside since I just was not sure the effort would
worth it. I think if you can appear to not be in eye shot, you could use it. I am sure it can work
in many situations but without the practice you could fail. They needed more practice sessions with
more people to be able to drill .