sys-power/nut includes a nice NUT Monitor GUI in scripts/python directory. There should be an option to install it in ebuild (perhaps a "monitor" USE flag?).
Created attachment 503408 [details, diff] nut-2.7.3-r1.patch A possible ebuild patch for installing nut-monitor through client use flag. Only tested that program run, I didn't do any others tests.
sys-power/nut-2.7.4-r2 has introduced the NUT Monitor GUI via "gui" USE flag so I am marking this bug entry as resolved now.