I wrote a driver for the Texas Instruments INA219 current and voltage monitor (used in, for example: https://www.adafruit.com/product/904). I’m often surprised that stuff like this doesn’t exist already. I found a couple of Python implementations but for something as simple and “lowly” as reading bytes of I2C and spitting them out on a ROS topic, Python consumes a bit much in terms of resources. I have especially users of e.g. Raspberry Pis and other small embedded hardware in mind for this. Same for the other I2C nodes I posted recently.