The only tool settersI saw in 40 years as a prototype machinest, instructor and master machinest are the ones supplied with the Hardinge lathe. They are simple and well made.
Now after all my working years I rarely used anything to set the tool hight. You can usually tell by the way the tool is cutting. When facing you'll leave a stub if you are too low and if you are too high you won't be able to cut to the center.
The "Calibrated Eyeball" is often used and being within a few thousandths is close enough for most jobs. When you are doing precision work and need to be "very careful", that's when you use the scale against the round part of the work or something on the tailstock that is on center.
Another trick is when you are facing a part and cut low, reset on the small remaining stub by eye and you'll be very close to "on center".