Amazon Price Change Notification Toolbar indicates availability of APCN, and will engage Price Watch in one click.
Amazon Price Change Notification Service (APCN) watches prices at Amazon Webstore and notifies user if price change meets user conditions. Conditions configuration is flexible, and includes prices for new, used, collectable and refurbished Store Items.
APCN Service works for Amazon-affiliate web stores as well.
) "APCN IE Toolbar - Click to enlarge screenshot")