In most states you can use a radar detector for personal use to avoid speeding tickets, and there's really not much your car insurance company can do about it. A radar detector alerts the driver when it picks up signals emitted by radar equipment that police use to catch speeders. The idea is for the warning to sound before the cop points the radar gun at you. Ranging in price from about $35 to more than $500, even a pricey model would more than pay for itself if it kept you from getting a ticket and subsequent hike in your car insurance rates. Like any high-tech gizmo, radar detectors have gotten more sophisticated. Using GPS technology, some of today's detectors can calculate how fast you're going and then adjust their sensitivity to radar signals accordingly. You need long-range sensitivity when you're going fast and shorter-range sensitivity in town. Some radar detectors provide digital voice alerts, and some can detect laser as well as radar signals. Now that local governments are using speed and red-light cameras, some models come loaded with information about the camera locations, which you can update using a computer and Internet connection. Many of today's radar detectors also work in conjunction with smartphone apps.