Electrochemical indicators are configured to indicate a variable such as time and/or a temperature excursion. In some embodiments, the electrochemical indicators comprise an anode layer and a cathode layer which contact an electrolyte to activate each indicator. In some embodiments, the electrochemical indicator comprises an electrically isolated RFID chip and an RFID antenna which are placed in electrical communication in response to the external variable. The completed RFID tag may then be read by an RFID reader. A completed RFID tag may also be incorporated within the electrochemical indicators comprising an anode layer and a cathode layer and where the RFID tag is unshielded and becomes readable as the indicator expires.