Apart from spatial-division multiplexing optical fiber communication system, seven core fiber has been widely investigated for optical fiber sensing application, such as high temperature, strain and vibration sensors. In this work, we further explored the application of seven core fiber on both conventional industry community and popular healthcare area. On one hand, a novel optical fiber torsion sensor was designed using tapered seven core fiber and demonstrated to measure torsion angles with tunable sensitivity, which can achieve as high as 1 nm/°. Moreover, the proposed torsion sensor owns the ability to discriminate the rotation direction with stable performance. On the other hand, based on the interference between the center core and surrounding cores in seven core fiber, an optical fiber interferometer was proposed using conventional sandwich structure to monitor the vital signs and activities of patients on bed. Respiration signals can be obtained and on bed/off bed/body movement activities can be recognized using this seven core fiber-based interferometer.