Smartphones already provide a vast toolkit in your pocket, and soon that arsenal could include the ability to take down a violent attacker.
No, not a new app, but a cunningly crafted case, initially designed for the iPhone 4, that includes a 650,000 volt stun gun.
Named "Yellow Jacket" after a species of predatory wasp, the case has its own external battery, capable of giving the smartphone up to 20 additional hours of standby capacity.
Inventor Seth Froom was inspired by an armed robbery at his home in which he was caught unarmed and unable to fight back.
So he came up with the idea for Yellow Jacket because most people have their mobile phones with them, wherever they are, whatever they are doing.
While the Yellow Jacket may not go down well with ultra style-conscious iPhone users, it does provide desperately needed battery life and could be a life-saver too.
That's assuming of course, users will have time to release the safety catch and a rotating electrode-cap that have been added to prevent misfires.
While stun guns are legal in the US, there is a fairly long list of countries where they are not, and you guessed it, the UK is on that list.
Elsewhere, Yellow Jacket's developers are looking for funding and are offering early bird specials for iPhone 4 and 4S owners. Versions for other models of smartphone will follow soon, they say.