A self-contained electronic monitoring unit for attachment to a device, such as a water filter, designed to be used until the occurrence of a predetermined event such as a predetermined number of uses, includes transducer for providing distinct outputs such as different audio output signals. A programmed integrated circuit and use detecting means such as electrical contacts detect each use of the device and monitor when the device is operational, when the end of life event is imminent and has occurred. The integrated circuit is programmed to operate the transducer to produce output signals during each use of the device informing the user that the device is operational, that the predetermined event or end of useful life is imminent and that the useful life has expired. The unit includes a battery for supplying power to the transducer and integrated circuit.