Compliance modules for fluid dispensers are disclosed herein. Exemplary embodiments of the compliance modules include a housing, a processor, memory, wireless communication circuitry and voltage monitoring circuitry for detecting a change in voltage of a dispenser power supply. The processor, memory and voltage monitoring circuitry are located within the housing. A connector for electrically connecting the module to a power supply of the dispenser is also included. The compliance module receives power from the dispenser. The processor determines a dispense event has occurred as a function of a change in voltage detected by the voltage monitoring circuitry. The processor causes the wireless communication circuitry to transmit a signal indicative of a dispense event.