I agree with you, and think this is a totally illegitimate use of government authority and taxpayer funds even if it were completely on the up and up. I would assuredly sue if I had any standing to do so and hope that someone does.
"well your honor it's like this... I spotted this punk-er-kid driving around not far from the mall, and noticed that he used his signal light. So I pulled him over see? to give him a prize - yeah! that's it! i was gonna give him this prize for good driving.
after a half hour of checking his license and registration, I found out that it was fifteen minutes after curfew, so I busted him for that...
then I saw a screwdriver in the back seat. We all know that screwdrivers are widely used in crimes, so I drug the little punk-er-kidlet downtown and after softening him up a tad, he confessed to murdering Jimmy Hoffa.
and his good driving was my reason for stopping him in the first place."