There are lots of useful tools for electrical work: multimeters, current clamps, and wands that light up next to a live wire. To this day, we really can't tell that much about the refrigeration circuit. The pressure gauges in your manifold are coarse, and they can't show the smaller things like sucking small slugs of liquid. Your thermometer tells you the suction line temperature, but you've got to find the right line on your wallet card that tells what pressure for R-407C gives 45 degrees dew point. But the card only has values for 40 degrees and 50 degrees, so you have to take a guess. Or do you say that the 76 psi you remember for R-22 is close enough, since you are doing a drop-in replacement with R-407C for it?
There is no reason why smart tools can't solve these refrigeration circuit problems. That's why I'm excited to share my invention with you.