1. In a personal computer-based home security system implemented as a software program that runs on commercially available personal computers that include a modem, a microphone, and a video camera, a method for monitoring an environment to detect and remedy unusual circumstances that occur in the environment, the method comprising: sampling data collected by the microphone and video camera to detect threshold events that represent a change in the environment; detecting threshold events that represent a change in the environment; conducting a close surveillance following the detection of a threshold event by more frequently sampling data collected by the microphone and video camera in order to detect, characterize, and record events that represent differences between the sampled data and data normally collected from the environment; using data patterns that define and categorize types of events; during close surveillance, monitoring and recording audio data input from the microphone and video data input from the video camera, detecting differences in the input data from expected background, comparing the detected differences with input patterns to determine the type of event that produced the differences, and computing a metric that describes a suspicion level corresponding to the detected events; and when the close surveillance component has detected sufficient events, initiating an appropriate remedial action.