Devices and methods for generating an alert for a vending machine are disclosed. A method of generating an alert includes monitoring a bus for at least one communication from the vending machine controller via the bus. The bus is then monitored for a response to the communication from a peripheral device to the vending machine controller via the bus. The response from the peripheral device is then processed. An alert is then generated based on the processed response. A peripheral device for generating the alert includes a bus interface configured to receive data from the bus and to transmit data onto the bus, and a processing unit coupled to the bus interface, the processing unit configured to process data received from the at least one other peripheral device and generate an alert based on the processed data.