Nowadays, telemonitoring is a new trend with huge potential of providing patients with innovative medical solutions to improve the quality of their treatment. In this paper, a new elbow flexion and extension rehabilitation telemonitoring wearable device using inertial and Electromyography (EMG) sensors is presented. The proposed system not only allows remote monitoring of the elbow joint angle but also provides information on the muscle activity of the main muscles involved in elbow flexion and extension, biceps brachii and triceps brachii. This new approach can help to monitor the musculoskeletal conditions that affect the elbow joint movement in order to obtain a wider frame of reference to improve the diagnosis and treatment of elbow rehabilitation. The hardware system relies on signal processing, data collection and wireless transmission through Wi-Fi communication of the measured inertial and EMG signals from a patient to a Personal Computer (PC) where a physician can monitor remotely through a graphical user interface. All stages from design, implementation and preliminary testing of the wearable device are presented. The measured flexion-extension angles and electrical muscle activity demonstrate that our device is reliable.