Getting a ticket can take a huge bite out of your wallet. I'm sure you are careful and safe driver. (Aren't you?) Nowadays though many municipalities are installing red-light cameras and speed-cameras to generate revenue, by catching you unassumingly disobeying the law.
Luckily there is a solution. It's called Trapster! How it works is that you load the software onto your cellphone or GPS device. Trapster maps show you where all the red-light cameras, speed-cameras, and cop hang-outs for catching people speeding. It will alert you if you are driving up to one of these Traps!
Essentially Trapster is a online version of a friend warning you about a speed trap. Accept it's used by thousands of people, and those people warn you. This does cause some issues, as sometimes it's not completely accurate. Sometimes a person might mark a red-light camera that isn't there. Of course the concept is still pretty cool.
The best part of Trapster is that it is Free! Also it's completely legal. Some states have banned the use of Radar Detectors, but no such law exists for sharing Speed Traps online!