according to Rustybrick (maker of many Torah/Jewish apps) one is allowed to bring their iPhone/iPod touch into a restroom, just be careful not to read any of the content while there.
(1) What is the Halachic status of the Siddur when the device is NOT displaying the text?
(2) Even when the text IS visible, is that different than a printed text in a book?
To answer the 2nd question first: Although a text displayed on a LED
screen is not considered a Halachic text (i.e. one may not use such a
text for a mezuzah- sorry iPad Torah) - it is not appropriate for one
to have the text displayed in a restroom, for it may cause him to
think about or say what he is reading, which is also prohibited in an
Concerning the 1st issue, since the text on the iPhone is stored
internally on flash memory drive, it’s not considered a Halachic
writing at all. At best, is electronically charged ones and zeros
which has no sacred status whatsoever. So, to answer our original
question – You may bring your iPhone/iPod touch into a restroom, just
be careful not to read any of the content while there.
Being as this is their business, I'm sure they've done lots of research into this topic, and even have a "contact us" on their website where can get the exact sources they use for the ruling:
For sources and further discussion, please feel free to contact us.
I actually emailed them and will update when they respond, but until then- here are 2 gedolim quoted in blogposts who suggest that digital writing is not writing:
Maran Rabbeinu Ovadia Yosef zt”l- quoted in this article
R' Shlomo Zalman Auerbach zt”l- "Shooting electrons is not considered by the Torah as writing" cited in this article