A method to arm an airbag, the method including determining, by a system device (106), that an arming condition for the airbag has been met; delivering a communication to a master device (102) from the system device (106) to inform the master device (102) that the arming condition has been met; snooping the communication by an expansion device (106); and arming the airbag by the expansion device (106) in response to snooping the arming condition.