I have not tried these, but looked at the web site and watched the video. You say that a mate has one, why don't you borrow it and see for yourself.
The principal makes sense, but each person is so different. Some are more sensitive to energy work than others. I could see this working really well for certain people and not working at all for others.
If you've ever watched the movie "What the Bleep Do we Know" you will discover that the results you get from most anything depends on what intention you have going in.
Your mileage may vary!
I'd be interested to hear what your experience is with them if you do try them.
