I don't know if that's the kind of answer kyle's looking for, but I feel like I should go sit in the corner for not thinking of it - cause that was my top choice in the favorite tools category!! Maybe because we're in the Theory section.
If that'll do what you want there's several different styles and brands that light up or make a sound when brought close to 'live' wires. They may be called 'Voltage Proximity Testers'
A lot easier than Kirlian Photography!
Fluke Model Shown Below
The Tip glows Red when close to a Live Wire.
[This message has been edited by Bill Addiss (edited 03-21-2001).]