Recently I was downloaded MapQuest 4 Mobile for my iPhone 4. This is Navigation App by AOL. There are so many free and Paid App for your iPhone to turn your iPhone into Navigation System. But I choose MapQuest 4 Mobile because it’s free.

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This is some Key Features that you’ll got on MapQuest 4 Mobile

• Free Voice Guided Directions: Alerts you of upcoming turns.
• Directions: You'll find the same trusted directions that you’ve come to expect from MapQuest.com.
• Drag & Pan Maps: Touch and drag, tap, and double-tap to change your map view
• Traffic: Add traffic and incidents to your Map with a simple tap on the Traffic icon
• Maps: View, pan, and zoom street maps.
• Find Me/Follow Me: Use your phone's GPS to find your approximate location and keep you centered on the screen as you move around.
• Local Search: Locate, call, or map local business with just one click.
• Map Toolbar Search: Tap an icon in the Map Toolbar to quickly get nearby businesses
• My Places: Create and save My Places routes on www.mapquest.com and retrieve on your iPhone.
• Off-route detection and Manual Re-route: Tap the prompt to re-route your original directions when you go off-route.

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And Unlike some other GPS apps, MapQuest 4 Mobile iPhone offers FREE voice guidance. Plus, you can search and call local businesses. There are also available on Blackberry, you can check it more details on MapQuest Page