For 911 purposes It's great. For professional (delivery, trucking, field service, etc.) purposes it's also a great tool. For the government to track your movements (or anyone else for that matter) it's scary.
Of course one of the issues with GPS is it's working off a satellite. You need line of site for the most part to get a good signal, and generally for proper coordinates you need more then one satellite. So in doors may not work, as well as wooded areas, under ground, etc.
If your really worried about it, you could simple cover your house in tin foil and keep the government from knowing where you are
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Charles Gallant