ESP8266 WiFi module
It seems I’ve been living under a rock for past couple years not to learn about ESP8266 WiFi module.
Long story short: last time I checked embedded WiFi options for hobbyists it was mostly $50-$150 boards or Arduino shields. And now there’s this tiny 10x25mm module for ~3 dollars (literally costs peanuts). Low power, but with fairly quick MCU, 1x ADC, 16x GPIO pins, WEP/WPA/WPA2 encryption, can be used both as client or as a WiFi access point(!). And most importantly has an amazing community, good software support, lots of info / documentation. Crazy! ;)