A novel motion detector utilising a millimetre-wave array front-end, with signal processing that mimics insect vision, is described. The use of passive millimetre-wave detection enables a significant improvement over optical or infrared wavelengths, when a colliding object is obscured by rain, steam or other aerosols. This, for instance, used as a blind-spot detector, will enhance driver safety in poor weather conditions. As insect vision techniques do not attempt to process an image, but rely on tracking moving edges, the processing tasks are less hardware intensive, resulting in a compact low-cost solution.