NB. The meters shown in the diagram are currently valued at; $3.26 USD on eBay
On the matter of the circuit, I should have noted that this particular design is not the most basic, but more specifically, aimed at DIY'ers looking for added telemetry and repeatability in processing. And so I'll definitely look into putting something simpler together for the less technically inclined.
With that said, you've raised some good points and I'd like to thank-you for taking the time to share your views and observations on this.