Price Protectr is a service that monitors online stores and alerts you to any changes in price within 30 days of buying a product. If it sounds simple it is, and frankly that's the way it should be.
Nobody likes finding out they could have saved money if they had paid attention to price drops, but it's easier said than done. Price Protectr does the work for you. All you have to do is give them the URL of the product you bought and your e-mail, and it will keep an eye on it for 30 days. If there's ever a change, you get an e-mail alerting you to the fact.
Price Protectr doesn't work with every online store. In fact right now it only works with ten of the major online retailers, and only for the United States and some of Canada. Nonetheless, it's a simple solution to the simple problem of human laziness. See also RefundPlease.