OK so dangerous means crime in your app then - but there are also many other types of hazard you could include - natural hazards, disease, terrorism etc. For so

OK so dangerous means crime in your app then - but there are also many other types of hazard you could include - natural hazards, disease, terrorism etc. For something like tornados I bet there's some great datasets available. You could also look at scraping news feeds - I've seen apps that extract place names from news data and geolocate based on the place. To an extent I think whether the app is worth building is is dependent on the data you have access to and any process you apply to enrich the data - these will govern the character and quality of your app. If you can give people something they cannot easily get elsewhere you might get more users.