The POOLGUARD Door Alarm with Transmitter will sounds immediately when the door is opened and the alarm will continue to sound until the door is closed and the alarm is reset, even if a child goes through the door and closes it behind them. The POOLGUARD Door Alarm is equipped with an adult pass through feature that will allow adults to go through the door without the alarm sounding. The alarm uses one 9-volt battery, (not included) with a battery life of approximately one year and is equipped with a low battery indicator that will audibly alert you when your battery is getting low. POOLGUARD is the only door alarm that is UL listed under UL2017 for water hazard entrance alarm equipment.
Price: $71.99 from poolproducts.com