A package in which a medical device is stored, the package comprising an outer shell providing a vapor barrier between an interior space inside the outer shell and an exterior environment, a medical device positioned in the interior space inside the outer shell, the medical device including a liquid-containing element that is subject to drying out as liquid from the liquid-containing element vaporizes and travels from the interior space to the external environment, a condition sensor comprising two metallic elements, each of the two metallic elements being composed of different metals, with each of the different metals selected so that the two metallic elements form an anode and a cathode of an electrochemical cell, each of the two metallic elements being in electrical contact with a conductive water-containing element, so that the water-containing element forms the electrolyte of the electrochemical cell, and an electrically conductive path extending from each of the metallic elements to a location wherein the electrochemical potential formed between the metallic elements can be measured to provide an indication of the degree to which the conductive water-containing element has dried out.