Can a user measure voltage with the 41-C series?

[TASP]

I probably couldn't put my hands on it right now, but I have a very similar voltage detector pen to this:

http://www.buyincoins.com/item/3476.html#.VTQZEiFViko

(I'm not pushing anyone to buy it, just an example of the technology available)

Anyhow, these things are SUPER sensitive. I can unplug an extension cord, and by using this pen tell which prong was the 'hot' as opposed to the 'neutral' just from the residual charge left on the wire.

I don't know how finely graded this technology could be made, these pens as made to distinguish 12V, 120V and 240V. The device has NO internal battery!!

If it is just a matter of scaling resistors (I don't claim to know how the pen works in regards to it's unbelievable sensitivity, the display is high electrical resistance LCD technology) a similar device could be made for the 4 to 6V range, and with the low current draw, the device could be a tiny strip taped on a calculator and reading out the batt voltage full time and not noticeably shorten the battery life.