Radar Detector's are soooo yesterday. Use your smartphone and get Trapster instead :
https://trapster.com. I use it all the time. Though its sold to help you navigate around problem areas, it's best feature is the speed feature. It alerts you to speed trap, cameras, hidden cameras etc, known police hiding spots, etc. I've never once got a speeding ticket since I started using it years ago, and it saved me from a big speeding ticket last summer on a road trip to Quebec city.