Useless (Score 5, Insightful)

As a long-time road cyclist I can say this is a completely useless product. Obviously if one is riding on the road one is going to be passed by cars. And so long as one is not an idiot listening to music while riding, one can *hear* vehicles approaching from the rear. This device can't discern how closely a vehicle is going to pass you, which would be the only useful information - warning you if the vehicle is going to pass, say, less than three feet away horizontally.