This is a great AppleT.
the most complete vernier caliper.
( metric n inch ) like a real one.
depth measurement

well done!

You can and should include  this into your list for checking out too. :)
Ejs open source Vernier calipers java applet with objects, help & 0-error logic

there are other good features to include.
your input field that you got me to understand how to make.