I've got a Go500 and the Grouped Camera Database (Permanent, Mobile, Temporary, SPECS, Traffic Light) and apart from the sounds (which I've got a program to edit them, soon!!) are a bit crap (Moo, Ding, Honk etc...) the warning distance can be specified to what ever you want!... (cost £2 per month!!) Dont' even think about using the TomTom database (its out of date!!!)..
Dunno it I'm alloud to say where from!...
All you do is dump the .ov2 and .bmp file into the Map directory to add the POI's!... that it!
with the new (Free) 'Home' software managing the TomTom range is now even easier!!!...
I think the Garmin specific database for cameras is coming allong, but its not as detailed as the TomTom one!!...