The link shortener should work on almost all Amazon pages, the exceptions being some heavily customized pages (like the Kindle page).

The tax calculator will work on most price fields, but first must be activated by the user by changing the TAX_RATE constant in the script to be a positive value (ex: 0.06 for 6%). In addition, it will only parse amounts in USD that are present when the page first loads.
Note: The tax calculator will parse all valid amounts, even ones that don't have tax. It is up to the user to know where tax is counted and where it is not. See Amazon's About Sales Tax page.