I got a magnet from a hardrive an mounted behind my dresser. It works great to hold my XD9. I had my Mossberg on there held with the second magnet from the hard drive. It works real good for the XD as I don't have a holster for it with the Streamlight on there. I am not sure how much weight it can hold... Pretty dang strong though.
I know that doesn't answer your question regarding that specific product, but I like the idea behind them.