I've made a little script for Blender. It measures the distance between active object (in 3d view) and the cursor. Use with Maj-SKey-Cursor to Selection.

A tutorial for understand scripts : http://perso.wanadoo.fr/jb.perin/ScriptPython/TutorialBlenderPython.html(fr)

Here is the script's code :

"""
Name: 'Distance'
Blender: 241
Group: 'Object'
Tooltip: 'Measure the distance between active object and the cursor.'
"""

# The Distance 0.1
# by :
# Pascal Isman (lascapi)

from Blender import *

print "--------------------"

obj = Object.GetSelected()[0]
cur_pos = Window.GetCursorPos()
obj_pos = obj.getLocation()

dist = (cur_pos[0] - obj_pos[0])**2 + (cur_pos[1] - obj_pos[1])**2 + (cur_pos[2] - obj_pos[2])**2
norm = (dist)**.5

print "The distance between ", obj.getName(), "and the cursor is ", norm

And here is the file : monscript.py(fr).