Livesafe[1], although not as straightforward or elegant, is a general life safety app that already does this and is already somewhat well-established. (This counts as a plug, I guess, since I know people who work on that app)
I like simple apps that do one thing and do it well, so I build Kitestring to give them a little friendly competition. I'm hoping that it's simplicity / ease of use will be attractive to people.
I think there are many people who could benefit from an app like this. Of course I'd like them to use mine, but I'm also happy to see them using another app as long as they're on top of their safety.