The short answer:

NotifyPrice is a free service that sends you an email/notification when the price of an item you want goes down.

The long answer:

Say there is an item you want, but you are not ready to buy it, the price is higher than you'd like to pay or you purchase an item regularly and want to catch a deal on it. That is what we are here. We want to help you save money. So find an item on a website. Copy the URL and paste it into the bar on the NotifyPrice home screen. Fill in your email address and start monitoring. You can leave it as simple as that and you will receive an email if the price goes down even one cent. If you would like to adjust when and how often you receive notifications you can do that through advanced options. You may also adjust settings for an item while viewing it in your lists. Click on the "My Watches" button to see all the items you have added. Here you can adjust the price you want to be notified at or below, set an expiration for the watch, make notes about the item, see the price history since you added it, etc.