Hmmmm.... let's see what we have here: Fifty cents worth of plastic sheet stock, maybe three bucks worth of machine time to cut it to shape, fifty cents for a burned DVD with custom graphics printed on it. Maybe a buck for packing materials etc. That a five-dollar bill of materials. Retails for $24.95. I love an outrageous profit margin... but only when I'm on the other side of it. Sorry... the hazard of being a product developer.
From a martial arts standpoint, there is some merit here. But all it shows you us that a hard object is a good thing to have in your hand. And if it has some sort of point or edge to it -- it doesn't have to be sharp -- where it will focus force, that's even better. Hitting someone with your hand is like hitting someone with a pillow because your hand is made of soft tissue; your hand is better than a pillow, of course, but you get the idea. Your own soft tissue absorbs and distributes some of the energy of the blow. But hitting someone with a hard object is like... well... like hitting someone with a hard object. The hard object doesn't absorb or distribute the energy your muscles generated; it transfers that energy to your target much more effectively. "Brass knuckles" are the perfect example of this. The same thing is true of simply applying pressure.
You can, as this fellow has done, make some optimizations in the shape of the hard object. But, getting back to product-developer-thinking, perfect is the enemy of good enough. You probably already carry some objects that are good enough. Instead of spending money for this optimized hard object which you will then have to add to your EDC list and will have to deploy quickly from wherever you carry it in a crisis situation, spend some time thinking about how the objects you already carry and would likely have at hand could be used.
For example, in the picture on the website of the woman with the terrified look on her face being attacked by the man in the oh-so-evil-looking hooded sweatshirt, she is backed up against her car presumably in a parking lot. If she was being attacked as she was about to get into her car, she would likely have her car keys already in her hand at that moment. That's a hard object which will work fine as a weapon and it's already in her hand.
Get in the habit of getting your keys out and in your hand before you leave the building. This is a perfectly natural and totally non-suspecious-looking thing to do which will draw no attention at all and yet it means that A) you won't spend vulnerable time in a dark parking lot rummaging through your bag or pockets looking for your keys, and B) you will have a hard, weaponizable object in your hand as you walk to and get into your car. Perfect. But, right now, yes, right now, spend a few minutes thinking about and even practicing how to use your keys as an improvised weapon. And if you're a martial artist, why haven't you ever sparred with your car keys? (By the way, if you do have a go at some sparring with your car keys, bring a second set because you might break the first... hard learned lesson.)
