Go Warwalking to detect open WiFi networks with ESP8266
For fun, entertainment or just curiosity the act of "Wardriving" gained in popularity during the adoption phase of WiFi networks - to detect an open WiFi network and ... so forth. Folks would drive around with a laptop and a large WiFi aerial to accomplish this task.
However thanks to the inexpensive ESP8266-based modules you can now make a much smaller device that fits in the palm of your hand thanks to Ray Burnette.
The combination of the two and a power supply rounds the device off which will scan for open networks and display their SSID, for example:
Furthermore Ray has also documented a basic framework for Arduino-compatible WiFi projects using the ESP8266 which will prove useful for further experimenting.
So to get started, head over to the project on hackster.io. And if you're interested in making your own version, PMD Way can help you with the parts, such as: