MobileNavigator lane checkNAVIGON MobileNavigator for the iPhone turns an ordinary iPhone into a full-fledged turn-by-turn GPS device. I've used the mobile app on the iPhone 4, the iPhone 3G, the iPhone 3GS, and my iPad. (The app is also available for Windows phones, and it will soon be available for Android devices.) Check out these screenshots from the app, and read my review of MobileNavigator in the Smartphones blog.
The orange arrows show me that the three left lanes are safe.