A retrofit dispenser monitor (100; 200; 300a-e) comprising: a connector configured to connect the dispenser monitor (100; 200; 300a-e) directly to a dispenser (150; 250; 350a-b; 370a-c); a vibration sensor configured to detect the attached dispensing action of the attached dispenser (150; 250; 350a-b; 370a-c); a controller connected to the sensor; and a transmitter (104, 204); characterized in that: the connector being configured to connect the dispenser monitor (100; 200; 300a-e) directly to a dispenser (150; 250; 350a-b; 370a-c) such that there is physical contact between the dispenser monitor (100; 200; 300a-e) and the dispenser (150;250; 350a-b; 370a-c); the controller being configured: in a learning mode, to learn characteristics of a data corresponding to a dispensing action of the attached dispenser (150; 250; 350a-b; 370a-c) by detecting vibration signatures and associating those vibration signatures with dispensing actions; and in an operational mode, to monitor data received from the sensor and to recognize subsequent data signatures received from the sensor which corresponds to the learned characteristics in order to determine a measure of dispenser use; and, and the transmitter (104, 204) being configured to transmit data relating to the determined measure of dispenser use; and wherein the controller is configured to determine whether the dispenser (150; 250; 350a-b; 370ac) has been refilled based on received data. a connector configured to connect the dispenser monitor (100; 200; 300a-e) directly to a dispenser (150; 250; 350a-b; 370a-c); a vibration sensor configured to detect the attached dispensing action of the attached dispenser (150; 250; 350a-b; 370a-c); a controller connected to the sensor; and a transmitter (104, 204); characterized in that: the connector being configured to connect the dispenser monitor (100; 200; 300a-e) directly to a dispenser (150; 250; 350a-b; 370a-c) such that there is physical contact between the dispenser monitor (100; 200; 300a-e) and the dispenser (150;250; 350a-b; 370a-c); the controller being configured: in a learning mode, to learn characteristics of a data corresponding to a dispensing action of the attached dispenser (150; 250; 350a-b; 370a-c) by detecting vibration signatures and associating those vibration signatures with dispensing actions; and in an operational mode, to monitor data received from the sensor and to recognize subsequent data signatures received from the sensor which corresponds to the learned characteristics in order to determine a measure of dispenser use; and, and the transmitter (104, 204) being configured to transmit data relating to the determined measure of dispenser use; and wherein the controller is configured to determine whether the dispenser (150; 250; 350a-b; 370ac) has been refilled based on received data. the connector being configured to connect the dispenser monitor (100; 200; 300a-e) directly to a dispenser (150; 250; 350a-b; 370a-c) such that there is physical contact between the dispenser monitor (100; 200; 300a-e) and the dispenser (150;250; 350a-b; 370a-c); the controller being configured: in a learning mode, to learn characteristics of a data corresponding to a dispensing action of the attached dispenser (150; 250; 350a-b; 370a-c) by detecting vibration signatures and associating those vibration signatures with dispensing actions; and in an operational mode, to monitor data received from the sensor and to recognize subsequent data signatures received from the sensor which corresponds to the learned characteristics in order to determine a measure of dispenser use; and, and the transmitter (104, 204) being configured to transmit data relating to the determined measure of dispenser use; and wherein the controller is configured to determine whether the dispenser (150; 250; 350a-b; 370ac) has been refilled based on received data. in a learning mode, to learn characteristics of a data corresponding to a dispensing action of the attached dispenser (150; 250; 350a-b; 370a-c) by detecting vibration signatures and associating those vibration signatures with dispensing actions; and in an operational mode, to monitor data received from the sensor and to recognize subsequent data signatures received from the sensor which corresponds to the learned characteristics in order to determine a measure of dispenser use; and, and the transmitter (104, 204) being configured to transmit data relating to the determined measure of dispenser use; and wherein the controller is configured to determine whether the dispenser (150; 250; 350a-b; 370ac) has been refilled based on received data.