Your kids take your car out, you either:
a) Let the tracker log to a file where they went, how fast they went etc and review it later
b) Use their phone or leave yours in the car to transmit the location
You like to race, do time trials etc, you use the logging mechanism to record and compare your laps, races etc.
You like to compare the most efficient way to work, record the tracks and compare.
Two additional elements that are key here,
www.motionbased.com has a great facility to view and compare tracks.
www.gpsvisualizer.com can be called with lat/lon as parameters to display a location. This can be made into a very easy dynamic link from the database where you log the info.
Chris.