One of the Bravo's in my company uses one in place of a shotgun catch (attached with bungee as previously mentioned but to retain it when not in use). I havent see it used in that manner, although we found a good (read: humorous) use for it:
When conducting pistol reload drills, if he brings the pistol in nice and close before dropping the magazine (M9 metal mags) the magazine will drop and be sucked in and stick to the magnet. Voila: dual purpose shotgun catch / dump pouch. We have a promo video of these and are trying to figure out what cool paint scheme to use before selling to the Airsoft crowd...
