MAX1704X
Arduino library for the MAX17043 and MAX17044 LiPo Battery Fuel Gauge. For an example of this device on a breakout board see the SparkFun LiPo Fuel Gauge.
This device is also available on breakout boards from Amazon. Be cautious when ordering these from unknown suppliers. After reading on various forums that some of these do not work properly, I decided to order a clone. My experience was exactly as described by others - they simply do not work! I recommend ordering from SparkFun.