Navigation device technology has advanced to a degree that makes these devices useful for the average user. The best navigation systems are the ones that are installed in automobiles, but these types also have several drawbacks. They are expensive, adding as much as $2,000 to the price of a car, and users are unlikely to have the devices when they most need them, which is generally when they are driving rental cars in unfamiliar locations. Add-on systems are represented by phone handsets and dedicated navigation devices. Verizon Wireless and other phone service vendors include global positioning system (GPS) circuitry in their handsets, and they offer services that provide maps and navigation information over the phone. Dedicated navigation devices have been relatively expensive, but due to a price war among manufacturers, their prices have been dropping significantly. These devices generally come with maps and touch-sensitive displays that can be mounted on a car windshield or dashboard. Nearly all of the products use the same SiRF Technology GPS chips and NAVTEQ or TeleAtlas maps, which means there is little difference in the performance of the devices. Nearly any Palm or Pocket PC can be transformed into a navigation device by adding software and a Bluetooth GPS receiver. The two-piece approach is not elegant, however. For lighter duty, a new cell phone with navigation capabilities may be the best option.