Retrofittable vehicle collision warning apparatus

A retrofittable collision warning apparatus for vehicles comprises a base unit within the vehicle cabin and a plurality of remote units located around the periphery of the vehicle. The remote units generally operate in a low-power sleep mode, and periodically go partially active to listen for wakeup inputs from the base unit, at which time the remote units enter a highest-power active mode to measure the distance between the vehicle and obstacles in the proximity, and use wireless transmission to communicate obstacle position information to the base unit. The base unit accepts operator commands, use wireless communication to transmit control signals to the remote units and receives obstacle position information from the remote units, communicates obstacle position information to the operator through audio and/or visual signals, and controls operation of the collision warning apparatus. The base and remote units employ power conservation and voltage boosters to extend the lifetime of compact, low voltage on-board power sources and communicate through wireless means. Auto detection and configuration of remote units are incorporated for easy system expandability.