I installed a digital voltmeter, just a cheapy, not for looks but for utility, on my wires I have on the tank bib, for my audio players. Got it at Autozone, maybe $10, made to plug into a lighter socket but I just removed that, wired it direct and put velcro on the back. Not pretty but effective. With all my juice use and with a 1.3kW alternator, keeping an eye on the volts is necessary. This one has a digital readout as well as idiot lights to grab your attention - and the display is lit. I do have it on a switch which I forgot to throw for this picture.
