The battery tray indicators I’ve tried on Linux so far only seem to take the instantaneous power consumption into account. Is there one that estimates remaining battery life based on power draw over a longer time window and integrates easily with my desktop environment’s tray?
Not going after a bug though, it’s just the way the included battery meter in Xfce (and other X11 battery indicators I’ve found) works, while things like Android track usage over time to give a better estimate.
But based on the other responses, it looks like I’ll have to cook it up myself.