One thing to keep in mind as you visualize using a carrier-branded GPS tool on your cell phone: Each of these applications varies somewhat depending on the capability of the phone. For instance, on a little flip phone Sprint Navigation might not be able to do everything you can do with the same app on a BlackBerry.

You're also going to be in for a surprise when you go to out-of-the-way spots or head off-road. Much, if not all, of the GPS functionality depends on having a network connection. That's because all three phones rely on data on their respective carrier's server as well as the GPS. Each time you search for a business, ask for a new route, or need a traffic report, the wireless connection gets the new data.

The good news is that the data generally is current, which might not be the case for the points-of-interest database stored on an older dedicated GPS device.

If you're out of range of a cell tower, though, you can pretty much toss the cell phone into the glove compartment. We got excellent reception in metropolitan areas, but in , a camping spot on the central coast of California, we were dead in the water. This limitation is a major drawback for cell phone GPS applications in comparison with in-the-vehicle or dedicated GPS devices such as the Nuvi, which need only GPS satellite reception to work. (It also makes me wonder: How come Jack Bauer in 24 never has this problem with his cell phone?)

Talk to Me, GPS