OK, I think I'm onto something. they are known as Satellite based tracking systems for parents of teenage drivers. the following link highlights possible advantages. notice the amount of $$$$$ the police are putting into the case trying to defeat the teen driver.

http://www.autoblog.com/2009/09/18/report-parents-of-teen-with-speeding-ticket-fighting-citation-w/

doesnt work, they have a precedent that says the officer can use his judgement, no device whatsoever and still ticket you for speeding, and it will hold up unless you find a way to discredit the officer, that will almost assuredly backfire on you in the court.

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1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

Then just pay the silly ticket and don't waste the time and effort, what do you want me to tell you?