As mobile robots experience increased commercialization, development of intuitive interfaces for human-robot interaction gains paramount importance to promote pervasive adoption of such robots in society. Although smart devices may be useful to operate robots, prior research has not fully investigated the appropriateness of various interaction elements (e.g., touch, gestures, sensors, etc.) to render an effective human-robot interface. This paper provides overviews of a mobile manipulator and a tablet-based application to operate the mobile manipulator. In particular, a mobile manipulator is designed to navigate an obstacle course and to pick and place objects around the course, all under the control of a human operator who uses a tabletbased application. The tablet application provides the user live videos that are captured and streamed by a camera onboard the robot and an overhead camera. In addition, to remotely operate the mobile manipulator, the tablet application provides the user a menu of four interface element options, including, virtual buttons, virtual joysticks, touchscreen gesture, and tilting the device. To evaluate the intuitiveness of the four interface elements for operating the mobile manipulator, a user study is conducted in which participants' performance is monitored as they operate the mobile manipulator using the designed interfaces. The analysis of the user study shows that the tablet-based application allows even non-experienced users to operate the mobile manipulator without the need for extensive training.