The tools need to be affordable and easy to use. Compact tools are easier to display and ship. For faithful continuous measurements, the tool would need very precise elevating it costs. You can see how much the digital KMC costs.
... If you want to pursue it a scientific level, the field is open.
...
KMC's digital checker is a vastly overpriced tool, it is nothing more than a $15 digital caliper fitted with flat tips and a spring.
On the other hand I agree that these tools has to be affordable.
As I have mentioned in my post my objective here is mostly scientific. I like to know a confirmation with proof that these tools are overestimating the wear. It would also be good to see if someone can advise a precise way of measuring the wear.