Telemetry of energy, how can we go beyond instantaneous sampling

[viric]

I would like to use Meshtastic to measure energy use but the current "instantaneous sampling" is quite limited because the sampling period is not even fixed.
If I want to sample the use of energy of some device I need to sum how much energy it has used (by means of some integration), and that will be an ever growing number which could be in Joules or Wh or similar.
It would be like:
1 day 0h ago - 234 mWh
18h ago - 240 mWh
5h ago - 254 mWh
25min ago - 260mWh

Then the UI should be able to display a plot of the derived sampled signal.

I'm ready to do the firmware part and eventually some day someone can implement the UI part. How does this sound?
Can we add some "float ch1_energy" to PowerMetrics for this purpose?