Recently I had written a post about prizepinx, a tool to get alerted of price drops of items you find on online shops.
Here is another tool that does something similar. Shoppingnotes.com.
On the Shoppingnotes homepage you can activate a price alert just by entering a product URL and an email address. The website also provides a bookmarklet that you can add to “Favorites” in IE or “Bookmark” in Firefox. The bookmarklet allows users to surf the web as usual, and whenever they see something interesting, they can save the product image/price/description into their personal ShoppingNotes with just two clicks.
Within the shoppingnotes they can sort and organize all the products in many different ways. Most importantly, they can set price alerts on any product. Users will be notified by email once there’s a price change (any price change or only below a price that the user sets).