Feature Request: Ruler Tool

[Stiggles]

A ruler tool to measure distances and vectors between two points would be very useful. Proposed functionality:

Button with a "ruler" icon. When clicked, the mouse cursor turns into a large circle with a compass along the outer border.
If the user click and drags the mouse, a line will appear on the map that measures the distance between the first click and the mouse's current position, along with the direction and inverse direction to that point. (Example: 100.0 km, 170/350).
When the user releases the mouse, the line and the measurements disappear.
The ruler mode will remain on until the user clicks any icon or presses "Esc".

Possible extra functionality:

• a checkbox that appears next to the button that would use two clicks to designate points instead of a click and drag. on a third click, the line and measurement would be erased while a new one is drawn.
• a circular measurement mode for estimating ranges. Would act the same as the ruler, but would draw a circle with the center at the initial point in addition to the line.

For a more complete example of functionality, see: Silent Hunter's navigation map mode.