Led Power Meter

[projectwhat]

Ok So some of you probally know that I am making a guitar hero guitar / Frets on fire guitar. But I would like a meter that tells me how much power is left. Someone suggested just having one LED so the brighter the more power the dimmer the less, etc. But I was wondering if something like this would work:
http://store.qkits.com/moreinfo.cfm/FK101

I know its for audio but would it matter???

And could it be tweaked to work on a smaller scale with 4.7V down??