1btn is a Battery Powered Open Source ESP8266 WiFi Button - CNX Software
Trammell Hudson ✪ on Twitter: "ESP8266 ran for one hour while sending 1 Hz packets on WPA2 with a 150mAh LIR2450 coin cell battery. https://t.co/koKnHtBjg1" / Twitter
How to build an open WiFi finder using ESP8266 and two coin batteries - Use Arduino for Projects
Soldering on a lithium coin battery (button cell)? - General Electronics - Arduino Forum
Single Cell Boost Converter Circuit using Coin Cell – 5V Output