An apparatus comprising:a proton battery configured to generate protons in the presence of water to produce a potential difference anda first pair of electrical contacts electrically connected to the proton battery to enable a flow of electrical current therebetween when the potential difference from the proton battery is applied across the first pair of electrical contacts,wherein the apparatus is configured such that when the apparatus is attached to the skin of a user, the proton battery is exposed to water from the users skin which produces the potential difference and enables a flow of electrical current through the users skin via the first pair of electrical contacts.
