As alternatives to the hybrid case and in-car headrest mounts we've previously seen for the iPad, Gripdaddy's new Headrest Mount ($80) and Arm Mount ($90, aka Gripdaddy Arm) for the iPad offer two similar solutions for turning iPads into backseat video players. Both accessories use metal, rubber, and thick acrylic plastic to hold an unencased iPad on a flat, padded surface with a spring-loaded tension arm, attaching to one headrest with adjustable…