For me it would just be something to get an idea of battery level if I happen to be not plugged in somewhere. There are times where I go to storage for a couple hours to work on the 5er and it would be nice to be able to glance at a meter like that and know the battery voltage. I have a spot where I'd like to put one but couldn't imagine running a wire directly to the battery from that location. Grabbing an existing 12v wire near that location would be much preferred to running something to the battery.
Thanks for the info.