When creating models (replacement parts or parts that interact with real world objects), I find myself measuring a lot parameters in the ‘real world’.
While calipers are still the most valuable tool for that, I simplified a lot of it by simply taking a picture of the object with a ruler in the same focal plane; then wrote a little tool that allows to draw simple lines and use that ruler to declare a known reference length - then all lines can be measured accurately enough for many uses. Also: angles between lines. Very simple, but pretty useful.
Pull requests welcome.