Here is a cushion that provides your neck and back with ample support as you use your smartphone or tablet. The Utsubusene Lying Face Down Cushion Z has two parts to support your back and forehead respectively. Its iron frame can handle up to 220lbs of load.
You can use this cushion to play games while lying on your back or face down. The opening is adjustable up to 4.3″. You can also adjust the angle up to 35 degrees. More information is available here.