Wi-Fi Packet Monitors are usually a computer program or sometimes a piece of computer hardware that can be used to intercept and log traffic over a Wi-Fi network. My favorite software tool of all is the popular Wireshark which I have used several times for hacking Wi-Fi based hardware, like integrating the common Wi-Fi smart socket with OpenHAB. Packet monitor tools give the possibility of seeing what type of data is being sent out by a wireless device and provides us with the chance of conjoining that data for our purpose.
Apart from the use of software for packet capture, we can also leverage hardware for this. The Espressif Systems ESP8266 and the ESP32 modules have been a go-to module for a lot of makers regarding Wi-Fi/IoT applications. Stefan Kremser aka Spacehuhn who first launched an Esp8266 based packet monitor, earlier last year has released an improved opensource ESP32-based packet monitor which is available on Tindie and Aliexpress for purchase.
The original Packet Monitor board put together by Spacehuhn is based around the ESP8266 and allowed you to see data packets flying around you in real-time. It tells how many Wi-Fi packets are sent every second and on which channel. It is also able to display the result on a small OLED Screen. The ESP32 version comes with some new features.
Then new ESP32 Packet monitor includes some new features to the existing ESP8266 Packet monitor. It adds an SD card support for capturing and saving traffic data with the possibility analyzing that data at other time, unlike the ESP8266 which shows only the current packet only, the ESP32 version displays an average RSSI (Received Signal Strength Indicator), and of course offer an improved performance due to the increased power of ESP32. It is built around the ESP32-Wrover module, which has 4MB Flash and 4MB PSRAM.