I know you're asking for a voltmeter, but thought i'd put in a plug for "BackOff" LED monitor: http://www.signaldynamics.com/products/Modules/HUVM.asp
And installed: http://advrider.com/forums/showpost....6&postcount=28
So far it's working great. Just enough to get my attention, but cheap and discreet installed. It's been educational to see how V drops when idling and how even turn signals being on can make a difference!
"If you hold a cat by the tail, you learn things you cannot learn any other way."