Sorry. If you use the latitude and longitude from the LocationSensor, reverse geocoding is easy. If the latitude and longitude come from an outside source (as you are getting from your raspberry) , your options are as indicated in the link.
All the options I am aware of are mentioned in the Reverse Geocode link posted earlier. What you want to accomplish is not easy, it requires advance coding skills Try some blocks by creating a basic app that takes a latitude and longitude from text and use the Google api, post what you tried and someone might provide specific advice.