Just leaving a comment here, if you are an electrical engineer and you are interested in working on thing like this, I'd love to talk to you.
I'm making a very reliable and professional $2 power meter.
We make our own microcontroller to replace the $0,03 Padauk.
To prove our microcontroller we build better 18650 battery chargers dischargers and power meters.
Also a remote monitoring system for the even more reliable analog power meters. https://www.youtube.com/watch?v=P_3DXcB9-xE
We also make other cheap but reliable $0,30 moisture and sound sensors and $3 wearable carbon cloth infrared heaters.