Abstract: A system for deterring the placement of a foreign substance in a user's beverage and for alerting the user to such attempts including a sensor that detects movement or agitation, such as an accelerometer, contained in a substantially flat housing, preferably configured to provide a surface on which a coaster and/or a beverage can rest. Said system includes means for the sensor to transmit data to a processor that is enabled with software capable of communicating with an external device or activating an alarm system associated with the housing.