A reminder apparatus and method are employed to by a dwelling occupant to provide a reminder concerning a pet's whereabouts. The apparatus features a carrier member that is adapted to hang from a door knob or handle, and a timer device is supported on the carrier member and operable to indicate expiration of an interval of time from a selected starting point. When the occupant lets the pet outside, they activate the countdown function of the timer and an alarm sounds when the countdown expires, providing a reminder to let the pet back inside the dwelling. Indications of an indoor and outdoor status are provided on opposing sides of the carrier member, so that reversing of the facing direction of the carrier member every time the pet transfers between the indoors and outdoors results in an ongoing accurate indication of whether the animal is inside or out.