A lot of people have used ESP8266 to add inexpensive WiFi connectivity to their projects, but [Oscar] decided to take it one step further and program an Arduino over WiFi with the ESP8266.

You have an ESP8266 board like the Wemos D1, a Li-Ion battery ... do pushbutton or sensor-driven wakeup, manage WiFi, and even read the battery voltage – all of these are a single line of ...