A magnetorheological piston includes a body having a substantially magnetically energizable passageway and a substantially magnetically non-energizable passageway. The monitor is capable of activating individual light emitters of an emitter array arranged in an electrical grid by driving at least one of row drive lines and at least one of column drive lines of the electrical grid. A heating medium is placed in the container and is made from material heatable by electromagnetic conduction. In some embodiments of the method, a trigger that is controlled by the patient is detected.