There is one that will copy the value to the clipboard:

http://kyticka.webzdarma.cz/3d/moi/#CurveLength

And there is one that will provide a readout while drawing:

http://kyticka.webzdarma.cz/3d/moi/#CurveLengthBeingDrawn

I think if you need a value between "2 points", you'll have to break the curve at the 2 points.

[EDIT] Foiled again by you and your wabbit! [EDIT]