In some embodiments, an apparatus includes a substrate, a power source, a connector, electrical circuitry, and an electrode assembly. The substrate has a first surface and a second surface different than the first surface. The power source has a positive terminal and a negative terminal Each of the positive terminal and the negative terminal are coupled to the substrate. The power source is configured to provide power to an external stimulator coupled to the apparatus. The connector is disposed proximate to the first surface of the substrate and is electrically coupled to at least one of the positive terminal and the negative terminal of the power source. The connector is configured to electrically couple the external stimulator to the power source. The electrical circuitry is coupled to the substrate. The electrical circuitry is configured to electrically couple the connector to at least one of the positive terminal and the negative terminal of the power source. At least one of the connector or the electrical circuitry is configured to prevent a short circuit of the electrical circuit. The electrode assembly is coupled to the second surface of the substrate. At least one electrode of the electrode assembly is configured to contact bodily tissue and to facilitate transmission of an electrical current through the bodily tissue.