Abstract: A method of remotely detecting rule violations at an outdoor site according to one aspect of the invention includes installing a self-contained VMU at the outdoor site near ground elevation, including affixing a chassis of the VMU to a permanent mount. The VMU is operated in a low-power standby mode that includes passively monitoring an ambient magnetic field at the outdoor site to detect a disturbance caused by a presence of a substantial ferrous object. In response to a detection of a disturbance in the ambient magnetic field, the VMU exits the low-power standby mode and initiates an active operating mode. The active operating mode includes operating a video camera by the VMU to capture video data; and wirelessly transmitting a signal representing at least a portion of the video data to a computer network. The video data is received by a remote node in the computer network via the computer network, and stored in association with a database record.