If anyone is interested, I made a current and voltage datalogger based on an ESP8266 and the INA219 breakout board.
It allows very fast logging to follow power consumption over time in mAh and mWh. It consist of the arduino code and also C# code for the PC.
Logging is done to CSV files that can easily be graphed or plotted in Excel.
The project: Wifi Current/Voltage Datalogger – Cron Blog – My personal findings
