US personal finance start-up Wallaby has launched an iPhone app that tells users which credit card they should use in which shop in order to get the best rewards.
Customers, who sign up with an e-mail and password, enter details of all of their credit cards in the app which acts as a cloud wallet.
When they enter a store, Wallaby uses geo-location to identify where they are and runs through the cards to see which will provide the best deal in terms of cash-back, loyalty points and discounts.
The app - which will arrive on Android by the end of the year - offers an almost identical service to one launched earlier this month by Glyph.
It launches as the company admits that it is struggling to meet demand for its main product, the Wallaby card, which users link to their credit cards and then swipe at the point-of-sale, with the transaction automatically charged to the best option.
Says a blog post: "We have not been able to scale our product as rapidly as we had originally planned for and have had to ask our tens of thousands of anxious future customers to wait patiently for us to deliver them their Wallaby Card."