Radar detectors have become a driver's way of minimising the chances of being caught for speeding. A radar detector is, in fact, a boon for those who inadvertently exceed the speed limit. Using a radar detector when driving might also act on the psychologically to alter driving behaviour.
Radar detectors are devices that can identify specific traffic radar signals from radar speed measuring devices utilising dedicated frequencies - in Australia these are K and Ka radar bands. A radar detector can detect and alert to the presence of a radar signal via voice and/or tone alerts. Other radar transmitters such as automatic door motion-sensors can also trigger an alert from a radar detector. These are known as false alerts. Some radar detectors with GPS can learn to filter out fixed false alert locations further improving your driving enjoyment.
However, please note that VASCAR technology (police measuring speed by following using a calibrated speedometer) cannot be detected by any radar detector. Many fixed speed trap and red-light camera locations cannot be detected as they transmit no radiated signals. Radar detectors enhanced with GPS may have the capability of alerting to the presence of a fixed camera location nearby. (ANPR or piezo sensor operated - Fixed Speed and Red-light speed cameras are typical of these).
The choice is up to you. If you drive frequently and inadvertently exceed the speed limit radar detector is a must. You may not require a radar detector should you drive at or below the posted speed limit/s.
When you buy a radar detector for your vehicle, it's essential that you keep in mind what you are buying, from whom you are buying it and the reputation they, and their products, may or may not have.
You might find radar detectors for a lower price on the internet; they might lag behind in fulfilling your requirements. There are many radar detectors available online and there are just as many counterfeit copies which share a resemblance in physical appearance and nothing else. The performance and quality of counterfeit radar detectors is inferior and you will have little or no recourse to the seller. For use in Australia as electronic devices, radar detectors must meet critical standards and each radar detector sold should have an accreditation mark for verifying suitability for use here.