Although things like NFC-enabled smartphones are making this less of an issue, the fact is that most of us still carry around a wallet full of credit, debit, loyalty or other cards that we routinely have to rifle through. That's why the Coin was invented. It's a single card-shaped device, on which all your other cards can be stored and accessed electronically.
Upon first getting the Coin, users start by attaching an included card-swipe dongle to their iOS or Android smartphone (or tablet), then using it to swipe their cards – they also use the phone's camera to take a photos of those cards. This process allows the information for each card to be stored on the phone, via a dedicated app. That data is then transferred from the phone to the Coin, where it's protected by 128-bit encryption.
The app also lets users add or delete cards, as needed. Up to eight cards can be stored on the Coin at once.
When users subsequently need to pay for something, they just press a central button on the Coin to toggle through the stored cards, with the name of each one appearing on a small LCD display. When they get to the one they want, they just swipe the Coin like they would normally, anywhere that regular cards are accepted – a chip-and-pin version isn't available yet, but it's apparently in the works.
The phone that was used to set up the Coin doesn't have to powered up, or in the vicinity. If you're carrying it with you, however, the app will alert you with an audio alarm if you walk away without the card. Additionally, the Coin will deactivate itself if it loses contact with the phone, after a pre-selected time span has elapsed.
An included replaceable battery should keep the Coin running for two years of "normal usage." The card is also shock- and water-resistant, and won't demagnetize in the presence of magnetic cards.
The designers of the Coin are now independently crowd-funding its commercial production. A pledge of US$50 will get you one, when and if they're ready to go. Shipping is expected to begin next summer (Northern Hemisphere), at which point the cards will retail for $100.
The Coin can be seen in use in the video below.