Ring That Rings Attacker's Bell
Redstart's new "Subtle Safety" Defensive Ring seems like an evolution of the "keys-between-the-fingers" technique. It even comes with a disclaimer:

"Our Subtle Safety™ jewelry is not intended to be used as a weapon or as an aggressive device; rather it is meant to provide its wearer with confidence and a subtle tool for self-defense. Any other use of our Subtle Safety™ jewelry is not recommended and can cause harm to
its wearer or any third-party."
Oh, those wacky attorneys!

If you can't take nail-clippers on an airplane, how long do you think it will take them to ban these? And what about school violence? Is zero-tolerance for jewelry the next step?

Sidenote...
Does it come with its own cleaning solution?
How DO you get blood off sterling silver?