Various robotic systems have been proposed to provide assistance in activities related to daily living and in physical therapy. Our consortium developed a prototype assistive robotic module, called the "smart mobile walker," which is a motorized walker. This robotic device was developed to assist with the mobility of senior citizens and persons with disabilities such as stroke survivors and people with spinal cord injuries. A pilot study was performed with four senior citizens to evaluate the usability of the system relative to a commercial walker. The participants performed a "10-meter walk test" (10MWT) with either the smart mobile walker or a commercial walker on flat, upward-sloping, and downward-sloping surfaces, indoors over five days. An electromyography (EMG) signal and the heart rate were recorded, and the gait parameters including the speed, cadence, stride length, and gait cycle duration were measured to evaluate the system usability. The participants performed better with the commercial walker on the flat and upward-sloping surfaces owing to the unit's light weight. On the downward-sloping surface, however, the speed control offered by the smart mobile walker was found to outweigh the advantage of the light weight of the commercial walker.