This is a proof-of-concept application that can be managed and updated on an ESP8266 using resin.io.
It uses an Adafruit Huzzah Feather board and OLED FeatherWing to charge a battery and show the percentage of charge.
Circuit info and inspiration for the meter is from here: https://learn.adafruit.com/using-ifttt-with-adafruit-io
resin.io ESP8266 code is from here: https://github.com/resin-io-projects/esp8266