A baby's eyes are naturally drawn to things in motion. By watching moving objects a baby learns to coordinate his eys to move at the same time. Therefore, a little time looking at a mobile that moves is some great infant stimulation, especially for a newborn.
To make this interactive you can manually move the various parts of the mobile and talk about what you are doing. "Mommy is moving the moon to the left and back to the center." "Daddy is moving the bear to the right and now to the left."