Citibank has introduced ‘price rewind’ where you can register a Citibank-issued credit card and they’ll search for price drops on the items you purchase. When a price drops $25 or more you can apply for a refund of the difference in price.

This is especially interesting to me because about a month ago I purchased something on Amazon for $185. Three weeks after my purchase the price dropped to $140. I thought I could get the difference credited to me, but I was wrong.

• Amazon at least used to offer a 30 day pricing guarantee. But multiple calls to Amazon at first yielded clueless agents who knew about no such policy, and other agents who confirmed that the policy is actually seven days. So I was out of luck and made no headway.

• American Express used to offer price drop protection, and became famous for iPhone payouts in 2007. But sometime after that stopped making that offer, so my payment with the Starwood American Express didn’t help me get the difference refunded.

Citi will refund up to $250 per item and up to $1000 per year in aggregate.

You do have to register your purchases individually at citi.com/pricerewind, including where and when the item was purchased and the price paid. I suspect that requirement will mean that most consumers don’t use the option, which will limit the costs of providing this. Which will also keep it generous and useful for those who do. (Just like how most folks don’t know about purchase protection, but it paid to replace the glass on my Samsung Galaxy SIII after the I dropped the phone on a sidewalk.)

They’ll search competing merchants for 30 days for a lower price, and notify you that you can request a refund (which will be sent by check rather than as a credit to the card account used to purchase the item, presumably because the offering is underwritten by an outside insurance company).