they work really well. just be careful not to do sessions for too long at the beginning. start out with 10 minutes or less just to be safe and then go very slowly.
don't listen to the people who haven't actually tried them.
the discoloration of the water has nothing to do with what is being released and many of the manufacturers readily say this.
the real scam is 'toxic hunger' ;)
try a session for yourself and you will know they work. sessions are about $20 dollars or so.