In-fiber Bragg grating (FBG) sensor technology has become one of the most progressing sensing topics of this decade in the field of optical fiber sensor technologies as FBG sensors are capable of measuring a wide range of parameters and have potential for simultaneous measurement of multi- parameters. In recent years, rapid progress has been made, in particular, in sensor system developments and applications. The fundamental aspects of the FBG sensor technology have been reviewed recently by the author. As a complementary article, this review paper concentrates on the recent progress in applications of FBG sensors for large composite structures, electrical power industry and medicine. Also, recent progress in sensor system developments associated with these applications are addressed.