I am working to develop a customized business concept to call a taxi. Where customers request a Taxi on smart phone app. Taxi drivers will have an Android GPS pre-loaded with maps to work off line. The Taxi driver is guided to the customer using voice navigation (for safety). Questions: * Where to find the latest maps to be used for Andriod GPS off-line. * Which software to use for voice navigation off-line. * Which software to use for off-line navigation directions from point A to point B.