+1. The low-tech version of this I've heard and I've been doing is:
Hold a printed white paper sheet right next to your monitor, and adjust the amount of brightness in monitor so the monitor matches that sheet.
This of course requires good overall room lightning where the printed paper would be pleasant to read in first place, whether it's daytime or evening/night
Which, fair that it may be obvious to others to just scan their eyes from screen to paper. I've been surprised with how much people will just accept the time their eyes have to adjust to a super bright screen. Almost like it doesn't register with them.