The present invention relates to wearable devices. A wrist-worn sensor for measuring wrist tendon forces corresponding to specific finger motions is provided, the sensor comprising: one or more piezoelectric sensors, wherein the one or more piezoelectric sensors emit electric currents generated upon pressure from wrist tendons on the one or more piezoelectric sensors; and a processing module configured for converting the electric currents generated upon pressure from wrist tendons into signals and for processing the signals for identification of one or more specific finger motions. A method for detecting specific finger movements based on wrist-tendon forces is also provided.