There are one or two answers that come close to answering this question but they either fall short or go in straight at the deeper end.
Essentially, I am interested (for genuinely academic reasons!) in being able to record the number of active devices (cell phones, basically) in different locations in space/time. I absolutely DO NOT want to know what they are doing, who they are, or anything about the users, I just want to know a) how many phones in a given radius and b) if it helps, some sort of signal strength so I can normalise/measure how many devices are present in each locale.
1) Is this possible? I am half-decent with Linux, a rasp pi and a bit of Python... (factor that in) 2) What hardware is needed? 3) Any links to help me out on this topic?
I am not an infosec person at all, so this is a world I know little about... be kind :)