You can subscribe to data feeds from http://www.localdatacompany.com/ and combine those with mapping code (a programmer on eLance.com or oDesk.com should be able to do that for you fairly easily)
You mean like Google Maps does already? If I am understanding you correctly, then integrate your own app with a Google maps API or have a raw data port embedded directly into your generated pages.
It really depends if you will be using Google's business data or your own.