This site (https://patrickhlauke.github.io/touch/pen-tracker/) is sample app that shows how a web page can interact with a drawing tablet. It is also a good way to easily diagnose some tablet or pen problems.
Start using your pen on the site and you'll see some information in the upper left hand corder.
Source code for pen-tracker is here: https://github.com/patrickhlauke/touch/tree/gh-pages/pen-tracker
https://patrickhlauke.github.io/getting-touchy-presentation/ -