Already have my butt firmly planted in my 21st century seat with all the electronic devices installed on the trailer which includes a Trimetric battery monitor. I just choose not to go further when the analog/mechanical gauge works just fine. No batteries required and no need to change. 
It will be interesting to see, as you pointed out, whether there will be crosstalk when two of yous park next to each other at a rally. A problem "dinosaurs" need not worry about. 