Sygic uses maps that are "on board" - everything you need for navigation is sitting in your phone. Even if you are out of reach of any mobile operator signal, you can navigate seamlessly.

When you purchase Sygic Mobile Maps, you have unlimited right to use following data:
+ maps on your device, street level network
+ database of addresses
+ database of points of interest

You will not need to pay any additional fees to Sygic or mobile operator for navigation.

Go to iPhone webpage