A wearable device for sensing and transmitting physical activities of a user to a computing device is provided. The wearable device includes a first wristband worn around the wrist of the user, a left connecter assembly attached to the first wristband, a center assembly having sensors for sensing physical activities of the user attached to the left connecter assembly, a right connecter assembly attached to the center assembly and a second wristband worn interchangeably on the exhaustion of the primary battery inside the center assembly. The center assembly includes one or more sensors for sensing user activities. Examples of sensors include but not limited to heart rate sensor and the galvanic sensor. Further, the center assembly also includes a finger sensor to measure heart rate.