I have become fond of using the Massive Development Chart on my iphone for developing film in trays. By turning the brightness all the way down, turning the display red in the MDC ap, and keeping the phone on the other side of the darkroom I am not worried about fogging the film.
But I was worried about an incoming phone call lighting up the screen, so I developed the habit of putting the phone in Do Not Disturb mode. So imagine my surprise when her call came through this morning while I was developing! Fortunately the brightness and distance factors worked in my favor.
Some research informs me that "Do Not Disturb" is not actually enabled unless the phone is locked, making it difficult to use the MDC timer. A little more research informs me that "Airplane Mode" might resolve this problem, since it prevents the phone, email, etc, from working but allows the use of other aps. Gotta test it out first, but anyone else have experience?