Hi MrFlo,
As per your description, I can understand no need modification in the linux device driver of INA219 (assumed its working file), Just we need to play at linux application level, as I looked in to driver code, we have to just play with /sys/* file system. It is very simple task, just read relevant file from /sys/, it self give you value, so you can do it using shell script and simple C/C++ code.
Also I mentioned Milestone at 100%, so you have to pay once I finish complete task, enjoy