This feels eerily Soviet, since you would become fearful of your neighbor or brother turning you into the authorities -- with or without merit. I'm not sure it fosters the kind of society I'd want to live in.

although in theory this seems good, the last comment is accurate in that in practice it might not work. i do wish i had one of these though pretty much every time i drive.

A better solution: safety cameras; the euphemism for speed/red-light/seat belt cameras that grab offending license plates and issue citations.

I am a major civil liberties advocate and am very wary of impending "surveillance states", however, I think that safety cameras are a great idea. Road deaths number over 40,000 annually in the USA, and safety cameras would induce safer driving, saving thousands of lives. I would, however, want to make absolutely sure that the system meets two conditions:

(1) Non-offending license plates aren't recorded.(2) Citations themselves would be public record, but the location of issue would not. If you're speeding, you deserve a speeding ticket--not to have where you were made public record.