1) New Scale: "Spaces"
While games typically tell you a movement space is so-and-so many feet or miles or whatever, many don't bother with that during play, and simply speak in terms of the number of spaces a character can move, the range of a spell or weapon in spaces, and so on. That's what my players are used to, and having to convert back from feet to spaces is a constant little annoyance.
I work around this by saying one space is 1 foot, and having my players ignore the "ft" reference, but that's ugly. And while it's possible to simply count the number of spaces on the screen, the ruler would obviously be able to do this, too, if "Spaces" were one of the options under "Scale" in the Page Settings popup.
Alternately, you could just replace the pulldown menu with a text entry field, and let the GM type in whatever name or abbreviation he wants to use for an increment of movement.
2) New Ruler Option: "True Diagonals"
Without a grid, the ruler measures actual diagonal distances. This setting would make it behave the same way when there IS a grid. The only difference would be that when there's a grid, the ruler would snap to the center of the beginning and ending spaces.
3) New Ruler Option: "No Diagonals"
Not every game that uses a square grid allows diagonal movement. This option would measure distances as if the character could only move vertically and laterally. So moving up two squares and over 2 squares would be a distance of 4, not 2.
4) New Ruler Option: "1.5 Diagonals"
Some games that use square grids split the difference by allowing characters to move diagonally at the cost of 1.5 spaces of movement. So moving up 2 and over 2 costs 3, not 2. This option would make the ruler function that way.