The data comes from http://medicare.gov/hospitalcompare/search.html

It has a pretty good amount of useful data if you're interested in searching around :).

To answer your second question: I'm not. For the V1 of the app, I'm relying on the government data being valid. However, I'm currently building an in-app feedback form that will allow users to (a) report real-time wait times if they are in the hospital, and (b) report closed ERs / incorrect addresses etc.