System for monitoring physical activity

A system that monitors user activity, the system comprising:

• a wrist device comprising a curved body and an electronic circuitry supported by the body, the electronic circuitry comprising a first set of light emitting diodes arranged in a matrix form and forming a display unit, at least one motion sensor configured to measure physical motion caused by a user to the wrist device, a heart activity sensor based on optical heart activity sensing, and at least one processor configured to acquire motion measurement data from the at least one motion sensor, to process the motion measurement data into a motion activity metric, and to cause the display unit to display the motion activity metric, wherein the at least one processor is further configured to acquire heart activity measurement data from the heart activity sensor, to process the heart activity measurement data into a heart activity metric, and to cause the display unit to display the heart activity metric.