Reverse Geocoding Without Web Access

Question

I am working on an application where one of the requirements is that I be able to perform realtime reverse geocoding operations based on GPS data. In particular, I must be

Answer 1

I would stay away from implementing your own solution from scratch. This is a pretty big undertaking and there are already tools out there to do this. If you're looking for an open source approach (read: free), take a look at this blog post: Using PostGIS to Reverse Geocode.