A support includes a base having an outwardly extending projection with a passageway therethrough, and having a tag receiving portion configured to removably support a tag on the base adjacent one end of the passageway. A different arrangement involves a tag that includes a housing having an opening therethrough and having an annular surface around the opening, an annular gasket engaging the annular surface, and circuitry within the housing having a sensor located in the region of the opening and having a transmitter that can transmit wireless signals. A method includes defining a passageway that provides fluid communication between an interior and exterior of a container, supporting a tag on the exterior of the container, and causing the tag to sense, at a location in the region of an end of the passageway, a condition within the container.