By Tom Barlow, dealnews writer Perhaps you have a heavy foot and frequently catch yourself exceeding the speed limit without having any such intention. Or perhaps you feel (like I do) that sometimes it's safer to match the speed of traffic around you, even if that traffic is breaking the speed limit. Or maybe you just like going really, really fast. In any case, you might find yourself in the market for a radar detector. But will it do the job? What features should you look for? And how much should you expect to pay? Most radars employed by law enforcement use radio waves. Radar guns emit waves on a certain frequency, which hit your car and bounce back like a basketball from a backboard. The device can calculate the difference in the outgoing and return speeds of the sound wave (using the familiar Doppler effect) to determine your driving speed. Of course, this means that the gun has to have a clean shot at you, to make sure it's reading your car and not someone tailgating you. While detectors claim to work in many different frequency bands, there are really only three in common usage among U.S. law enforcement: X, K and Ka. Detecting one of these transmissions before you fall into the radar's clutches isn't all that difficult, because there is a great deal of scatter in it; like ripples in a pond from a thrown stone, the radio waves spread far and wide. While most basic radar detectors can do a good job of warning you about radio radars, another law enforcement device, the laser light gun (called LIDAR, for Light Detection and Ranging), is much more problematic. These devices shoot out narrow bands of light in rapid-fire fashion, reading the times it takes for the reflected light to return, and calculate your speed from those readings. The band of laser light is much more narrowly focused than radio waves, so there isn't as much scatter for detectors to read before you enter into the radar's kill zone. In fact, traffic radar expert Craig Peterson of RadarTest.com told dealnews that there isn't really a detector on the market that detects lasers fast enough for you to react before you're busted, despite what product manufacturers might claim. The most advanced radar detector units combat this type of radar by jamming the signal; although, that's illegal in some states. So what features are most valuable in a radar detector? Radars balance on a fine line between sensitivity and false alarms. Random radio waves from sources such as automatic door openers or even other radar detectors can drive you crazy if the detector identifies them as radar transmissions. The better devices can identify and suppress these rogue signals. A very useful feature of some allows you to program them to ignore false signals that you repeatedly encounter. For those of us concerned about keeping our eyes on the road, voice alerts are a common and beneficial feature. So look for a model that is easy to operate, with a display that is legible, even at night. Backlit buttons can aid in this. Since detectors have a problem identifying laser radars before you drive into their snare, some detectors include radar jamming technology that overwhelms the radar unit with return signals and renders them ineffectual. Jammers can also be purchased separately. Either way, this is a pricey option. The killer app in the detector world, however, is GPS-enabled. This allows the detector, using GPS satellites, to know where you are and calculate how fast you are traveling, adjusting its warnings accordingly. Some can also download databases of hard-installed red lights and speed cameras, and warn you when you are about to encounter one — a very useful feature. For those who love their GPS navigation, there are detectors that incorporate this, leading you to your destination while keeping you from getting a speeding ticket. The combined units aren't cheap, though. The market is a bewildering array of technical terms. If you've a taste for digging into them, there are a number of useful sites you can visit, the best of which might be RadarTest.com. You should also be aware that radar detectors are not legal in Virginia or Washington, D.C. Some states also ban the use of laser jammers, as previously mentioned. To help you start your shopping, here are a few interesting models ranging from the mundane to the sublime. There are many other fine models made by Valentine One, Whistler and others, but we've selected a pick from each category that you can get at a good price at major retailers. Beltronics Vector 955 This windshield-mounted unit is a simple-to-use detector that handles X, K and Ka radars under "favorable conditions," according to RadarTest.com, as well as laser, at a most reasonable price. Best price: Amazon at $138 with free shipping Cobra iRadar This new device from Cobra will appeal to iPhone lovers. It uses a remote radar detector that transmits its readings via Bluetooth to your phone. An app then takes that info and acts as the interface between you and the detector, warning you of trouble ahead. Best price: iLorica.com, $120 Escort Passport iQ This do-everything model combines the best features of a voice-guided GPS unit with a 5"-wide screen and a radar detector. It includes the Defender Database of speed and red-light cameras and allows great customization of warnings. It also includes a number of smart features, such as the ability to learn which signals are spurious and ignore them, and it knows when you're moving below the speed limit and adjusts warnings accordingly. Best price: Crutchfield at $650 with free shipping Escort Passport 9500ci If you're really, really serious about avoiding traffic tickets for speeding, then you might want to consider this system, which is to radar detectors what Manolo Blahnik is to shoes: very, very expensive. However, it combines all the best features, including state-of-the-art detection and enough laser jamming to frustrate the most dedicated officer. And it claims to be undetectable by law enforcement, useful if you stray into Virginia or the District of Columbia. I suppose if you're going to finally invest in that Lamborghini, a measly grand-and-a-half isn't much to spend to make sure you can keep it on the road. Best price: Amazon at $1,520 with free shipping Tom Barlow formerly wrote for Aol's WalletPop and DailyFinance, and in addition to his dealnews contributions, he currently writes about lifestyle topics for Forbes.com. You can follow him on twitter @tombarlow. You can also sign up for an e-mail alert for all dealnews features.