Ok, but why do that for railroad crossings and not any other type of dangerous crossing? Should we have these apps announce every stop sign, traffic light, and uncontrolled intersection you travel through for safety reasons?
If that isn't to become some sort of text-to-speech database dump about the area, there has to be a good theory of the conditions for what's worthwhile. And I sense that the natural conditions are the same as the conditions for putting up warning signs, reducing the speed limit, etc.