http://father.io/#BzJv1Q

Yeah, no, i can't imagine this going wrong. ever.
not with todays shoot first, think about asking questions wether or not he was a terrorist later.

Although, it is an interesting step in Augmented Reality technology, not to mention a way to get MMORPG'ers to exercise a little.

I had an idea for something like this with a Highlander theme, but the without the point and shoot FPS aspect.

That would be nifty, plays well off the fact that you would presumably be one of a few people playing the game in your city. Really captures that whole "They are among us..." vibe. The fact that the immortals tend to wander off to some secluded alleyway to have their fights could help cut down on the "freaking out the public" aspect as well--unless someone catches you.

Plus you can sense when another immortal is near. And it could use geolocation to forbid killing on holy ground.