In Texas the legal descriptions (metes and bounds) of property boundaries in deeds usually use the unit 'vara'. A vara is 33 1/3 inches or ~2.8 feet. In my experience, in order to draw parcels in Texas I have to keep a whole separate spreadsheet where I digitize the lengths in varas from the scanned deed and convert it into a different unit available in ArcMap. It takes a surprising amount of time. Wouldn't it be great if the Measure Tool and the editing tools had this unit for specifying length?