If you feel you will be more comfortable doing it that way, feel free to go ahead. The primary reason a physical script is suggested is that it would not have any distractions when you read the script.  If you want to use your phone or tablet, make sure to turn off all the notifications and every other form of distraction when reading the script. Further, you don't need to put the phone under your pillow as that would not be healthy. Just place it aside after done.