Meet the FireFighter Smoke Alarm Detector: a smart sensor that works with Interlogix Wireless Systems to let you monitor any UL smoke detector. When an alarm is detected, a signal is sent to the control panel that contacts the central monitoring system. The Firefighter has a multi-color LED to give you visual feedback. For instance, when sound from your smoke alarm is detected, the LED turns and stays yellow. Costs under $52 at this time.