Self explanatory I guess, if there were mobile phones we could use some functions such as the alarm and ringtones for distractions, the latter being the inferior due to the fact we could set the alarm for a specific time to go off, the ringtones would draw them close before you throw it so it really would be pointless for them. Also, some alarm tones (if it wasn't just the standard alarm clock sound) are louder than others so maybe you could choose volume of the alarm and draw a rough amount of zombies you want, say... 30, to any area, and not 100. Phones should really be a starting item, you can have a diary and to-do list, also there's earbuds so you could listen to music too? I searched and found some suggestions but that was then discussing the time period, well most phones (from the time period I read the game is roughly set in) had alarms and those annoying random songs no one likes to listen to.