Global Positioning System: Who's Tracking You?

We usually think of GPS (Global Positioning System) as a good thing, especially if we're using it to find our way from place to place. GPS satellites, radio signals, and receivers work together to pinpoint our location and get us to our destination. Hikers, bicyclists, and even golfers are finding ways to use GPS to improve their athletic experiences. The military installs GPS in many kinds of equipment, vehicles, and weaponry. GPS has surprising applications as well, such as tracking anima...