SIFT - Automatic Money Back
Sift will automatically calculate what is the optimal card to use for each purchase so that you get most out of your cards. With SIft you always know what card to use.
You can view this extension in Chrome Web Store here: SIFT - Automatic Money Back
Sift unlocks hidden credit cards benefits like price protection (which enables you to automatically get refunds when we find lower prices). They also support other things like return, warranty, theft and damage protection. Sift will not only detect the benefits available to you, but it will automatically file claims on your behalf with credit card issuers to get your money back.
I developed a chrome extension for SIFT that works in Amazon. It compares prices of the same product among different sellers and gives users the cheapest option. It also shows what credit card benefits are available when purchasing each product.