Modular robotics is one of the subfields of mobile robotics, which is emerging as a new trend in various sectors. Modular mobile robots can be reconfigured to perform a wide variety of tasks. In this paper, applications of modular mobile robots in various sectors such as industry, space, surgery, rescue and entertainment tasks are discussed. Based on the study, an improved design of a modular mobile robot for navigating through different terrains during a rescue operation is presented. Simulation study of the robot is included to demonstrate a motion capability of the modular mobile robot.