There are a few solutions available to consumers, ranging from sophisticated in-car GPS systems, which feature voice guiding, powerful dynamic route calculation, and the possibility to update the map from a CD.
Then there are handheld GPS devices, such as those from Magellan and Garmin, which store a map inside, and are usually designed for outdoor use. They cannot generally perform dynamic route calculation since they do not have any road information, and leave the user to find their own way from A to B.
Finally, a more recent solution has appeared on the market which uses the power of a PDA to run the actual GPS software, and uses the interface capability to attach a GPS receiver (antenna) to the unit. These tend to be the cheapest, easiest to use and most flexible solutions, but are only as rugged as the PDA to which they are attached.
Some recent systems can make use of a wireless Bluetooth connection so that they can be used both as a personal navigation aid and also inside a vehicle, by having several receives with Bluetooth capabilities, and a single PDA.