Tape Measure

Click to enlarge

This script started out as a reply to the question of how to assign a
shortcut to the tape measure, :) and I tried to find it in the customise
interface but quickly gave up and thought this would be a better
solution as it places the tape* for you and prints the result to the
text box and also copies it to the clip board.
*(although to their centres only atm which may be inaccurate
depending on how big your objects are and just where you want
to measure to)

This will at least speed up the process of measuring.

Pick the the two object you want to measure via the pick buttons
and click go and presto the distance between their centres is
displayed in the text box on the script ui.
It also places a tape measure between the two objects so you
can finesse the positions of the tape and its target.
You'll have to go to the  Modify panel to see the resulting
adjustment of any repositioning you do.

The measurement is also copied straight to the clipboard so
you can paste the result wherever you need it.

It also uses the units in your setup

Download from the link on the right >
Drag and drop into one of the viewports to install
- then customise user interface -
Lukes' Tools - TapeMeasure