Attached is a patch that adds the following to the email-ext plugin:

• Regression trigger: Applies when current build has more failures than previous
  build.
• Improvement trigger: Applies when current build has fewer failures than
  previous build.
• Added options to tokens:

• FAILED_TESTS: showStack option to suppress stack traces in the mail
• CHANGES_SINCE_LAST_BUILD: showDependencies option to show changes in
  projects the current project depends on

All of these have been tested and work on our Hudson instance.