Best for: People who need occasional navigation help and don't mind losing access to phone calls while using the device for direction information.Hardware tested: Apple iPhone 3GSNavigation app tested: Magellan RoadMate 2010 North AmericaPrice: $60 (United States and Canada)
The iPhone gives users instant access to a navigation system that offers many of the features of dedicated GPS devices (including the live traffic and weather information that two-way connected devices deliver).
The iPhone's built-in Google Maps app can provide directions, but it lacks interactivity and turn-by-turn directions. That's why, to maximize the iPhone as a navigation device, you need a specialized navigation app.
A smartphone makes a convenient navigator, since it's likely to always be with you. But using a smartphone as a navigation device has drawbacks, too. With the screen constantly on, your phone's battery can quickly exhaust its charge; in my testing of an iPhone equipped with navigation software, the device's battery life dropped by about 70 percent in just over an hour. At a minimum, you'll need to have a charger on hand to support this method of navigation.
In order for the iPhone to get a clear signal from GPS satellites, it needs to sit in a cradle on your car's dashboard or windshield. Basic mounts cost $30, but specialty mounts can improve the iPhone's performance as a navigation device. Both Magellan (for $130) and TomTom (for $120) sell mounting docks that provide power, an amplified Bluetooth speaker to serve as a speakerphone and to issue audio directions, and an auxiliary GPS receiver to complement the iPhone's GPS chip and improve signal reception. But when you add the cost of the mount to the cost of the app, the total expenditure approaches what you'd pay for a dedicated device with a larger screen.
Another drawback: Smartphones tend to be smart about just one operation at a time. Whenever I fielded an incoming call, the navigation application had to shut down; it would relaunch and resume navigation only after I completed the call. If you frequently travel to unfamiliar places, you'll be better off with a dedicated GPS device.