Check out this video from Cincinnati Children's Hospital Medical Center. They do a great job explaining some of the different ways you can access a dynamic display device.
Children with motor impairments can access dynamic display devices in a variety of ways. Any time a motor impairment is present, it is necessary to obtain an AAC evaluation by both a speech language pathologist and an occupational therapist to determine the best access method. Access methods may include use of a head-mouse, switch scanning or eye control. Video by Cincinnati Children's Hospital Medical Center.