but thats when you get speed ticket if you are driving too fast ! whether n900 detect the laser or not, unless you mean like a map remembers where the speed cameras are.

there is an application i don't recall its name but its on every phone on the planet except n900 (java - symbian - iphone - ....) where users puts the locations of the cameras they saw or know about it somehow and place it on the map, other users can rate this info how true it is (and there are many users so you will be sure about the cams in that location),,this map works in that application's gps with alerting voice, so its not just google earth there are many participants. your only shot is to use any java emulator to run that application.