Hi everyone,
I am looking for ideas on how to count the approximate number of people in a certain area (the length of the line in a cafeteria to predict waiting time, that is). My first idea was to passively listen into GSM communication, getting TMSIs of cell phones (almost everyone carries one) and count each above a certain signal strength. Unfortunately, sending intervals of cell phones in idle are way too long. Setting up a fake base station just strong enough that cell phones in a certain distance will try to log in and thus can be counted might work. However, even as unlike a full IMSI catcher the device would reject log ins so that phones would stick to real base stations hence not hampering communication (right?) or intercepting calls, this is still illegal (sending on a restricted frequency, forging identity, ...). Is there a less criminal way to force cell phones in a certain area start sending signals?
As there is a WiFi hotspot in the cafeteria, listening into WLAN communication and counting MAC addresses would work. However, probably there are not enough smart phones around yet and many people shut off WLAN and stick to 3G to save battery power.
Any other ideas? IR radiation, etc.?