Im gonna go ahead and say no on the radar detector. Well kinda...

I had a Valentine 1(one of the best) for a few years and it went off constantly in the city. It got so annoying i would turn the damn thing off!!! On the highway it was helpful so long as the cop was clocking cars in front of you. If your the first he hits or waits a while in between radars your SOL. It will sound off but by then your usually toast.

Playing devils advocate we had an srt-6 on our lot with one of those super badass built in radar detectors. Funny thing is i laughed at it at first. I turned onto the service road and went to the stopsign and made a right. I got up to about 55 in a 35mph zone and it screamed at me so i nailed the brakes. Low and behold as soon as i came over a hill there was a cop sitting there! It 100% saved my ***.

The only thing is from what ive seen cops use their radars spontaneously more often than they just sit there and let them scan. So for the $$$ im gonna say no.