I have finally had some success with tracking internet consumption
per client device, nice n cheap
Buy - GL.inet 1300 Router
Buy - 8Gb USB Key (not junk)
Note - The 1300 is Ethernet WAN. You'll need a second router for the 4G and double NAT. Tell me if you find a better method
And I can see consumption
by device per month. Yay.
Now I know who to kick for using all the 4G data.
Some hassles / bugs still to sort to make more reliable.
expert want to help me out - please PM me to solve a little weirdness.
I'll erase it and upload instructions later.