Drupal 7: Webform: Send Email Custom PHP on Webform submit
It's possible that you could use either hook_webform_submission_presave or hook_webform_submission_insert in a custom module, check for the your webform component value (i'd assume it's in $submission) and then fire your email.

In a custom module, add your hook like so.

function mymodule_webform_submission_insert($node, &amp;$submission){
  // Use devel to investigate the variable
  dsm($submission);
}


Creating custom modules for Drupal 7 or Drupal 6. Tutorial.

Use Devel module to investigate your variables, as seen in my example above. 

Jason.