1. A computer-implemented process for locating one or more persons in an environment, comprising: using a computer to perform the following process actions: inputting a sequence of contemporaneously-captured frame pairs, each frame pair comprising a frame output from a color video camera and a frame output from a depth video camera; using a face detection method and the color video camera frames to detect potential persons in a environment; using a motion detection method and the depth video camera frames to detect potential persons in the environment; and using detection results generated via the face detection method and motion detection method to determine the location of one or more persons in the environment.