"Based on consumer feedback, there is strong interest in reasonably priced GPS navigation systems on mobile devices," said Jim Greiner, VP and GM of MapQuest.

The service uses Sprint's existing location based services and GPS enabled phones to acquire wireless device location information. Since the maps are downloaded from MapQuest to the phone at the start of each journey, you never have to update the mapping information. The mobility of a cell phone means users can use the service not just in the car, but on foot, bicycle, unicycle, roller-skate...you get the idea. What else do you get?

• Audible turn-by-turn voice and visual directions, using GPS, straight from the phone handset
• Users can enjoy a seamless navigation experience while receiving phone calls
• Full pedestrian navigation mode that ignores vehicle turning and one-way driving restrictions
• Optimized routing calculation to find the fastest or shortest route, avoiding toll roads, highways or other specific elements
• High-quality dynamic color maps with zoom-in/out, pan and point on map functionality
• Easy address input for mobile phones;
• Intuitive location search for address, intersection or zip code, including unique "points of interest" category search capabilities
• Automatic re-routing without the need to contact the mapping server; and
• Front-loaded data retrieval within the cell coverage area allows for a seamless navigation experience within and outside of cell coverage areas
  

MapQuest Navigator uses mapping data provided by Telmap.

I'm currently in the process of reviewing a similar service from mobile GPS leader TeleNav, and will be able to compare the mobile phone based navigation experience to true in-car GPS navigation soon.