A device with single MCU-based motion detection, local alarm and supervisory arrangement for alarm system controlled by an alarm control panel (ACP) is disclosed. The device includes a sensor component to monitor environment, an output component to generate warning messages, a power supply component to provide power, and a microcontroller to communicate with sensor component, drive output component and monitor the status of ACP. The device can detect when intruders break in and make alarm warnings even when the ACP is destroyed. Plurality of devices and said ACP form a local warning matrix network (LWMN) to increase the detection area and scary effect to intruders. Each device of LWMN works independently when the ACP is destroyed.