I see both sides here. My main concern with this approach is the false sense of security it might create. In my experience , the separation of cities into "good" and "bad" areas is only valid in aggregate. I'd rather someone took precautions and stayed alert than happily sauntered through an area that the app told them was safe. I guess it's difficult to know if this strategy works, since you'll never know if you avoided a would-be encounter with a mugger.

With that said, I can't fault your motivations, and building it so quickly was a real achievement!