One embodiment includes a support configured to resiliently and removably grip a door hinge portion, with circuitry coupled to a wireless communication portion on an exterior side thereof. A different embodiment has a wireless communication portion with two antennas that is supportable on a container by a support so the antennas face in different directions externally of the container. Another embodiment has a detector on a support with a portion configured to extend through a gap between a door frame and a door, and has a blocking portion that can obstruct access to the gap and detector. A further embodiment includes a container with a wall and a movable door, and an antenna in a recess of the wall near the top of the container. Another embodiment includes a container with a door and a vent, and an antenna supported adjacent the vent.