Hi you can connect to an exteral GPS device using bluetooh and use its features such as mapping ur position, finding distances between places, finding best route to reach your destination etc.
Use of exteral GPS is that it can find may satellites quicker and you can map ur position also when you are practically anywhere on earth with or wothout your network operator being present.
All you need a is a GPS blutetooh module to run your servies which actully means that it bluetooth modules costs less, than buying an additional device which would turn heavy on the pocket.
See below website link for buying Bluetooh GPS Device and services in India.: