Ive seen a handful of these vids already. Not all can be explained by a hidden magnet in the armpit. One woman used both arms to try it first on one arm and then on the other arm. So any magnet would have had to be firmly secured. Plus, she pressed it on various spots on one arm and it did nit react until she git it over the exact spot. Which would not be possible if it was reacting to a magnet hidden under her armpit.

I don't know what is going on but I don't think it is a simple as a hidden magnet.