A system comprising: a continuous glucose monitoring, CGM, device and a wearable device for providing an alert to a user regarding the user's blood glucose value; wherein the CGM device has a glucose sensor and a sensor electronics unit comprising a transmitter that is configured to transmit glucose information about the user's blood glucose as a radio frequency signal in response to a trigger comprising a change in zone of a glucose concentration of the user between hypoglycemic, hyperglycemic and euglycemic zones; and wherein the wearable device comprises: a communication module configured to receive the radio frequency signal wirelessly from the transmitter of the CGM device; and an alert interface (504, 512) configured to provide a first alert when the user's blood glucose value is within a predetermined range, and a second alert that the user's blood glucose value is outside the predetermined range; wherein: the wearable device is configured to communicate with a network of other devices associated with other users; and the wearable device is programmable by the wearer to communicate with selected followers and, if the user does not acknowledge an alert, the wearable device is configured to notify the followers, wherein the communication module is configured to relay, using Bluetooth or Bluetooth Low Energy, the signal received from the transmitter to a display device in response to the glucose information meeting one or more predetermined criteria, wherein the wearable device further comprises an accelerometer to detect the wearer's activity level, and wherein: the alert interface (504, 512) is configured to output a visual alert if the accelerometer detects that the user is active; and the alert interface (504, 512) is configured to output an alert in the form of an audible tone, a vibration and/or an electric shock if the accelerometer detects that the user is not active. a continuous glucose monitoring, CGM, device and a wearable device for providing an alert to a user regarding the user's blood glucose value; wherein the CGM device has a glucose sensor and a sensor electronics unit comprising a transmitter that is configured to transmit glucose information about the user's blood glucose as a radio frequency signal in response to a trigger comprising a change in zone of a glucose concentration of the user between hypoglycemic, hyperglycemic and euglycemic zones; and wherein the wearable device comprises: a communication module configured to receive the radio frequency signal wirelessly from the transmitter of the CGM device; and an alert interface (504, 512) configured to provide a first alert when the user's blood glucose value is within a predetermined range, and a second alert that the user's blood glucose value is outside the predetermined range; a communication module configured to receive the radio frequency signal wirelessly from the transmitter of the CGM device; and an alert interface (504, 512) configured to provide a first alert when the user's blood glucose value is within a predetermined range, and a second alert that the user's blood glucose value is outside the predetermined range; wherein: the wearable device is configured to communicate with a network of other devices associated with other users; and the wearable device is programmable by the wearer to communicate with selected followers and, if the user does not acknowledge an alert, the wearable device is configured to notify the followers, the wearable device is configured to communicate with a network of other devices associated with other users; and the wearable device is programmable by the wearer to communicate with selected followers and, if the user does not acknowledge an alert, the wearable device is configured to notify the followers, wherein the communication module is configured to relay, using Bluetooth or Bluetooth Low Energy, the signal received from the transmitter to a display device in response to the glucose information meeting one or more predetermined criteria, wherein the wearable device further comprises an accelerometer to detect the wearer's activity level, and wherein: the alert interface (504, 512) is configured to output a visual alert if the accelerometer detects that the user is active; and the alert interface (504, 512) is configured to output an alert in the form of an audible tone, a vibration and/or an electric shock if the accelerometer detects that the user is not active. the alert interface (504, 512) is configured to output a visual alert if the accelerometer detects that the user is active; and the alert interface (504, 512) is configured to output an alert in the form of an audible tone, a vibration and/or an electric shock if the accelerometer detects that the user is not active.