And as you approach a known threat, you'll get an audio alert on your mobile device.
The developer of Trapster, Pete Tenereillo, said the system, which requires punching in a few keys such as "pound-1" to submit information to Trapster's database, should comply with laws banning talking on cell phones.
Tenereillo insisted he isn't encouraging motorists to break the law or drive dangerously, saying drivers who speed are bound to do so anyway.
And he said police officials he's talked to haven't complained about the service because it inevitably encourages drivers to slow down. (The International Association of Chiefs of Police did not respond to requests for comment.)
The free service can automatically detect location using mobile devices' GPS capabilities or tap their Wi-Fi and get location from a database run by Skyhook Wireless. (Skyhook sends trucks up and down streets to scan for home wireless routers or commercial hotspots and record the unique identifying code and location of each.)
Information about red-light cameras and where police tend to operate speed traps is kept in Trapster's database indefinitely. Information about active speed traps is kept for an hour, with the idea that officers may move on.
Users can choose the types of cameras or traps for which they want alerts.
To discourage pranksters and law-enforcement officials from flooding the system with bogus locations, users can rate others on the accuracy of their contributions, and those getting better ratings will carry more weight.
Trapster can be used with about 10 different wireless platforms, including Nokia Corp.'s smart phones, devices using Microsoft Corp.'s Windows Mobile and BlackBerry units from Research In Motion Ltd.