Harpinder Madan and his two co-founders started Slice a couple years back to focus on one very specific problem – the difficulty of saving and organizing online shopping receipts.

These tend to pile up in your email accounts, of course, and increasingly they include the records from offline purchases as well, from merchants like Apple and Macy’s.

Slice offers a solution. Its technology, once linked up to your email account, works in the background to extract all of the receipts, order confirmations, shipping notices, back-order messages – all of your post-purchase information – and presents it back to you in a format that is easy to save and act upon.

You can use it on the web, and as either an iOS or android app.

Over the recent holiday shopping period, Slice added a powerful new feature that alerts you when a merchant you purchased an item from lowers the price within a month afterward, which usually means you qualify for a refund.

“This has been the source of tremendous delight among our users this holiday season,” says Madan. “When you buy something, we continue to monitor the price of that item from the merchant for about four weeks or so, and if it drops we send you an alert with detailed instructions about how to get a refund.

“We put money in people's pockets they wouldn't have gotten otherwise. Most merchants say 'if the price drops in the next 30 days we will match it for you' but the reality is it's almost impossible for consumers to monitor that site for price drops.

“That’s very programmable for a machine, however. So while as a consumer you're never going to be able to do that well for yourself, for us it is easy.”

As often is the case at startups that pay close attention to user feedback, the idea for this originated with Slice users, who asked the company, since it was already monitoring their purchases, whether it could build in such a feature.

Slice also operates as an “ownership graph,” a concept we covered recently with our profile of Mine.

When it pulls the receipts and other data out of your email account, it actually gets everything from the past seven years or so, so right from day one it represents a rich source of data on your purchasing history and preferences.

Slice categorizes purchased items into a taxonomy – electronics, apparel, home & kitchen, etc.

While it has over 2,000 online merchants in its database, Slice has also developed a capability of recognizing the hundreds of thousands of smaller retailers out along the “long tail” of ecommerce.

“We have processed $1.5 B worth of purchases, 50 million items from some 500,000 merchants,” says Madan.

Unlike Mine, Slice is not a social shopping app.

“This is a service for you to manage your shopping information, not for sharing purchases with your friends,” explains Madan. “So if you sign in with Facebook Connect, we do not import your social graph. Our view is that users don't want to share everything, but are very selective.

“Thus, you can share if you wish, for example, you can track a package with a friend. We think people may want to share in some categories – travel, books, music, for example – and are working on a book sharing app now.”

Madan showed me how the massive amount of data Slice has accumulated about shopping patterns yields fascinating connections, such as how people who buy certain brands of gourmet foods will tend to also own a certain book and also favor one set of electronic brand, Apple, say, over another, like Samsung.

The company will probably eventually start recommending products to its users based on these anonymized data-mining insights.