Android phones, apps and tablets

turn. off. the. mobile. network!

Fair enough- why even bother taking it out of the house then?

Leave it on the side with all the radio chips turned off, screen off, no alarms, I reckon it would last a while.

You could use it to hold some paper down, in case a gust of wind disturbed them.

Big-screened dumb-phone at that point. 2g is best bet if you want to save juice, but I don't see the point of having a smart phone without a mobile connection