so when i got to dead city last night to upgrade the defibrillator, i noticed that i could click/activate certain ATM's throughout the area.. i only clicked a couple which gave me the white circle (activation), so I'm sure there are more things to do! seems like this seems to be the same type of process with a couple of the other secrets i have read about..

wonder what kind of easter egg this unlocks?!

ATM and vending machines give you money that about it.

some of them that let me click them did not give me money, but they did the second time through..

also, there were a couple computer screens i could click as well.. in the apartment complex part of it