Thanks for the post Bill. I saw this fellow at the Cow Palace today and he wouldn't state either way whether or not it it was legal to put it on a BB AR.
I did however think it spoke volumes that he only demoed his product on a featureless monsterman AR. When I asked him what use this was on such a gun - sine it could have a real mag release - he just shrugged.
I've seen magnet TOOLS before but they were sold and advertised as such. This thing is marketed as a solution and and not just a tool. There is dangerous implication in the message.