An intrusion detection technique involves: emitting a wireless signal within a container; detecting the wireless signal near the container; and responding to detection of a change in a characteristic of the detected wireless signal by transmitting a wireless notification to a location remote from the container. A different technique involves: responding to a determination that a condition representative of unauthorized intrusion is present while the container is stationary by transmitting a wireless notification; and responding to a determination that the container is moving by ignoring whether the condition is present. Yet another technique involves: monitoring whether a door of a container is in a closed position; and emitting a wireless signal indicating whether the container door is in the closed position.