Cell phones that tell you where to go

If you need directions only occasionally or don't want to carry around a separate GPS device, a cell phone with navigation capabilities might be a good alternative. Some cell-phone service carriers, such as AT&T, Sprint, and Verizon, are now providing GPS functions that can be accessed over their data networks through compatible GPS cell phones.

GPS cell phones' menus and features are similar to those of dedicated GPS units, including spoken and onscreen turn-by-turn directions, traffic info, and a point-of-interest menu. A key advantage of GPS cell phones is being able to get directions from a device you usually carry with you. And providers continuously update their databases, so you're less likely to get outdated information.

The service's cost is typically about $10 per month, or the service can be used for about $3 per day. That makes it easy to subscribe just for the period of a vacation or for one-time events.

On the downside, the small size of some cell-phone screens can make the map and directions hard to see. Smaller speakers compromise the audio quality of spoken directions, and small buttons on GPS cell phones are harder to use than on larger touch-screens. Expect to pay up to $50 for a mount, and you'll need a car charger for extended use. The navigation function won't work if you don't have access to a data network. And over a couple of years, that $10-per-month fee will add up to the cost of a stand-alone portable GPS unit that's easier to use and does not require a subscription.

Still, some analysts see cell-phone navigation growing. According to the Telematics Research Group, over 6 million phone-based navigation units are expected to be sold in the U.S. in 2008.

For more information portable GPS navigation systems, see our buying advice and Ratings.