A glass break sensor system for a vehicle having an on-board diagnostic ("OBD") link cable and an OBD port, the device comprising: a modular unit including: a pass-through OBD connector including an input connector configured to mate with the vehicle OBD data link cable and an output connector configured to mate with the vehicle OBD port; a microprocessor; a glass break sensor configured to detect a glass breakage event and generate an alarm signal when glass breakage is detected; and an audio alarm; wherein the input connector includes a power input configured to be coupled to a vehicle battery voltage input of the OBD data link cable and to provide power to the glass break system; and wherein the microprocessor is configured to: cause the audio alarm to sound when the glass break sensor generates an alarm signal, and wherein the microprocessor is further configured to: a) use OBD data to monitor whether the vehicle engine is running and automatically arm the glass break sensor when the vehicle engine is turned off and automatically disarm the glass break sensor when the vehicle engine is on; or b) use the vehicle battery voltage provided by the input connector which is configured to be coupled to the vehicle battery voltage input of the OBD data link cable to automatically arm the glass break sensor system when the vehicle engine is turned off and disarm the glass break sensor system when the vehicle engine is on. a modular unit including: a pass-through OBD connector including an input connector configured to mate with the vehicle OBD data link cable and an output connector configured to mate with the vehicle OBD port; a microprocessor; a glass break sensor configured to detect a glass breakage event and generate an alarm signal when glass breakage is detected; and an audio alarm; a pass-through OBD connector including an input connector configured to mate with the vehicle OBD data link cable and an output connector configured to mate with the vehicle OBD port; a microprocessor; a glass break sensor configured to detect a glass breakage event and generate an alarm signal when glass breakage is detected; and an audio alarm; wherein the input connector includes a power input configured to be coupled to a vehicle battery voltage input of the OBD data link cable and to provide power to the glass break system; and wherein the microprocessor is configured to: cause the audio alarm to sound when the glass break sensor generates an alarm signal, and wherein the microprocessor is further configured to: a) use OBD data to monitor whether the vehicle engine is running and automatically arm the glass break sensor when the vehicle engine is turned off and automatically disarm the glass break sensor when the vehicle engine is on; or b) use the vehicle battery voltage provided by the input connector which is configured to be coupled to the vehicle battery voltage input of the OBD data link cable to automatically arm the glass break sensor system when the vehicle engine is turned off and disarm the glass break sensor system when the vehicle engine is on. cause the audio alarm to sound when the glass break sensor generates an alarm signal, and wherein the microprocessor is further configured to: a) use OBD data to monitor whether the vehicle engine is running and automatically arm the glass break sensor when the vehicle engine is turned off and automatically disarm the glass break sensor when the vehicle engine is on; or b) use the vehicle battery voltage provided by the input connector which is configured to be coupled to the vehicle battery voltage input of the OBD data link cable to automatically arm the glass break sensor system when the vehicle engine is turned off and disarm the glass break sensor system when the vehicle engine is on. a) use OBD data to monitor whether the vehicle engine is running and automatically arm the glass break sensor when the vehicle engine is turned off and automatically disarm the glass break sensor when the vehicle engine is on; or b) use the vehicle battery voltage provided by the input connector which is configured to be coupled to the vehicle battery voltage input of the OBD data link cable to automatically arm the glass break sensor system when the vehicle engine is turned off and disarm the glass break sensor system when the vehicle engine is on.