Is there a way to switch the iPhone’s functionality to a phone-only mode. In this mode only incoming (and possibly outgoing) calls and SMS messaging would be activated. All other services (location, push, mail) would be disabled. So it would be just like your average seven-years-ago mobile phone which you could leave on during the night (*) without getting awakened by facebook push messages and without fearing to oversleep because the battery drained from downloading all the spam mails you got during the night.
Note that I’m not speaking of do not disturb functionality, which would also silence SMS messaging (which I’d still like to receive) and yet drain more power than needed by having activated location, push and mail services.
(*) alarm clock functionality should also work in that mode (but this could well be the built-in alarm, no other apps should be activated or running in the background)
Best Answer
You could turn off Wi-Fi (Settings -> Wi-Fi) and cellular data (Settings -> General -> Cellular -> Cellular Data) to get a phone which works just like a phone. Possibly disable location services (Settings -> Privacy -> Locations Services) as well if you really want to extend the battery life.
I do believe this would still allow local notifications, though, if you've got any apps that use them (such as some alarm or reminder apps).