An apparatus is disclosed for reminding a user of certain desired activity and for enforcing the performance of such activity. A clock generates clock pulses and a mechanism, such as a magnetic switch and magnet, is provided for detecting the performance of the desired activity and generating a detection signal when such activity is performed. A logic array is responsive to the clock pulses and the detection signal for selectively generating an electric alarm signal. In one form, the logic array is operable in response to the clock pulses to distinguish between at least two distinct time periods defined as an active time period and a dormant time period, and during the active time period, the logic array is operable to generate an electric alarm signal for a selected period of time in response to the absence of the detection signal. In the dormant period, the logic array will not generate the electric alarm signal regardless of the presence or absence of the detection signal. An alarm device, such as a beeper, is responsive to the alarm signal to generate an alarm that is perceivable by the user to indicate that the desired activity has not been performed. The alarm will continue for a sufficiently long period of time that it will irritate the user if he does not perform the activity that is desired. In one embodiment, the reminder is used to enforce the use of an orthodontic headgear. A magnet is mounted on the headgear and a magnetic switch is mounted in a mouthpiece which is fastened within the user's mouth. When the headgear is worn, the magnetic switch detects the presence of the magnet and will turn the alarm off during the active period.