OK, the headline is a bit misleading. This app won't kill you; in fact, it's designed to inform you about dangerous situations in your vicinity.
Lethal (click opens iTunes) from Elany Arts takes a location from either the iPhone's built-in location services or a list of 300 cities or parks throughout the USA, then provides you with a "lethal index" number. This number ranges between 0 and 400, with 400 being an extremely dangerous location.
The ranking comes from a composite of four scores based on lethal wildlife, crime, disease, and disaster probabilities in each area. The About screen for Lethal notes that the app is designed for informational and entertainment purposes only, so you should use common sense to guide your use of Lethal.
When I let Lethal determine the index for my home, I was surprised to see that it was 207 out of 400, or "somewhat dangerous". The wildlife index was rather high based on black bears and mountain lions in the area. Yes, we do see them on rare occasions in the area, but I'd be much more concerned about a neighbor taking a potshot at me than getting chewed on by a mountain lion.
Still, Lethal is fun (many comments are obviously tongue-in-cheek) and educational. Whether it's worth the US$1.99 introductory price is up to you. Check out the gallery below for screenshots of Lethal in action.