You could have 5 radar detectors in your car and it still wouldn't protect you as well as NOT SPEEDING! If you want something fool proof then just avoid the problem altogether. I'm not saying I never speed, but it's just so damn easy to leave 5mins earlier and cruise there rather than try to make up the time.

Little story from the past to put in perspective, the only time I ever noticed a mentionable decrease in travel time from speeding was when I decided to set a fastest pace from Fresno to Visalia. I cut the 45min trip into 28min, but had to book at 120 the whole way. I saved 17mins, which is approx. two cigarettes and a good solid crotch scratch, but if I hadn't been lucky enough that there just weren't cops on the freeway period, no dtector would have saved my ass from a ticket. And besides, poundin out 120mph on the freeway is just flat fuckin stupid!