The Rule of the Holy iPad
Sefarim (books of Torah learning) are considered holy and must be treated with utmost respect. We are cautioned not to place anything on top of a sefer (indeed sefarim themselves have a hierarchy of holiness, wherein a Chumash is placed on the top of the pile).
A person is learning from a tablet or a phone (see Halachah #439 on the use of such devices). Does the device attain the status of a sefer, so that if sefarim are lying around, the machine may be placed on top?
There is indeed leniency to rest a computer/phone/tablet on a sefer at the time it is being used for learning. However, if the learner takes a break or is temporarily distracted from the screen, the computer should be moved right away, because this leniency only applies when the device is actually being used for learning in the moment. There are some, though, who are machmir (stringent) and out of respect for the sefer always rest the device alongside it.