A friend had the app and did nothing but post local incidents to a group chat on a daily basis. We told him to stop or get the boot which he did. It illustrated just how uptight this app makes people. He wound up deleting it after a few months because it made him afraid to go outside as if he was surrounded by crime when in fact nothing had changed. (This is in south-west Queens NYC)

Bad things happen on a daily basis. These apps wont stop or deter crime. The best you can do is stay alert and aware of your surroundings.