“This is how I made a custom device to legally track people via their smartphones
Before getting into detail, this project was done legally within the legal limits, so please if you’re going to build like this then use it at your own responsibility :). It all started as a quick project for checking the connection status of my IoT plant sensors. I was studying my first year as an electronics engineer so I was pretty obsessed with making sure that anything could speak to the internet, or at least that’s what I tried :). While doing some research I had found that many people where using the so called “probe requests” frames sent by smartphones, laptops and wifi devices to announce the SSID they were connected to. In other words, your phone or laptop is constantly searching for all WiFi networks which you already connected in the past (unless you did remove as “saved”), sharing information to anyone who is listening for those public packets: where you have been before and your unique device MAC address.”