Coin is most practical electronic credit card yet

Coin can store up to eight credit cards on a single digital device, with users pressing a button to choose the card they want to use.

Coin

Cash, and even traditional credit cards, are becoming endangered. Thanks to Apple Pay, Google Wallet and mobile payment devices like Loop ChargeCase and Softcard, there are fewer reasons all the time to carry anything in your wallet. And now, after an unexpectedly long gestation period, startup Coin is launching its service. It wants to be the gadget that replaces all of your credit cards in a single device.

Unlike all of those other options, Coin is practical thanks to its familiar form. It looks and behaves just like a real credit card; it's exactly the same size, thickness and weight as your existing cards, distinguishable as something electronic only by a small e-paper display (which identifies the currently selected credit card) and a small button. The button is flush with the card's surface, making the whole contraption look like some sort of movie prop or pre-production prototype. Nothing this thin, this seemingly two dimensional, could possibly be host to a display, electronics, and battery, could it? The back of the card has a magnetic strip, your pre-printed name and space for your signature. It looks just like an all-black credit card, though it lacks any bank logos.

Using Coin is simple. Press the button to wake it up; if your phone (iPhone or Android) is nearby, it unlocks via Bluetooth. You can use the default credit card or cycle through any of the eight other cards held in memory. If your phone isn't around, you can unlock the card using a personalized Morse code-like tap sequence. Then swipe it, or hand it to the cashier to be swiped.

All that said, it's this final moment -- the swipe -- that is critical. I've written about a number of mobile payment devices before, and in every case you need to carry a backup credit card with you for the occasional point-of-sale credit card reader that simply won't work with the newfangled gadget. Unfortunately, Coin is no different. On my very first day with Coin, it only worked about half the time, failing to be read by a parking meter, ATM and in a grocery store.

In every case, a backup credit card saved the day, which begged the question: Why bother with Coin at all?

In subsequent testing, I've found that Coin is just a little finicky, and sometimes persistence pays off; the card will often read on the third try. And at least in my own personal experience, cashiers who seem confused by the all-black, no-logo, electronic card seem to have less success swiping it than cashiers who barely notice it's different, and simply swipe it the ordinary way. My success rate is now probably well over 90%, and I haven't had to pull out my backup card in days. If this batting average holds up, Coin will indeed be relevant, since it's easier to handle just one card and program it on the fly to act like a different card with the press of a button.

Coin also purports to be more secure than a traditional card, at least under specific scenarios. No, Coin doesn't support EMV chips, which many credit card companies are switching over to starting this fall. But Coin is far safer than a traditional magnetic strip card if stolen or lost. Without your phone or knowledge of the tap code, the card is a useless inert hunk of plastic, with 256-bit encryption protecting the various cards stored within. It doesn't even display credit card numbers.

How rugged is Coin? After all, it's the thinnest electronic device you'll own, and it needs to fit in a wallet or purse and be subject to the kind of daily abuse you'd subject a credit card to. Coin claims you can keep it in your wallet and sit on it, though it shouldn't be bent. In my wallet, it developed a worrisome crease after just a few days of normal use. I moved it to a different part of my wallet, where it could lie flat, and the problem appears to be solved. The battery is designed to last for about two years of normal use, after which you need to replace the Coin entirely (to the tune of about $100). It's likewise an expensive investment if the magnetic stripe should stop working prematurely or it befalls some other ignoble fate.

Setting Coin up is pretty straightforward. After pairing Coin with your phone (a one-time operation), you use the included credit card reader, which plugs into the phone's headphone jack, to swipe your credit cards into the mobile app. After authorizing the cards within Coin (essentially, proving you're their actual owner), you're good to go.

At this point you can store your credit cards somewhere safe and just rely on Coin, or carry a card in your wallet as a backup, just in case. And Coin works not just with credit cards, but anything with a magnetic stripe, including loyalty and membership cards. Coin can store only eight cards at a time, but the mobile app has unlimited storage, and you can swap them around at any time.

So is Coin the new universal credit card that should replace all of your existing plastic? As much as I'd like to say yes, it's probably not. I suspect that most people won't see the value in spending $100 for a universal card that only works about 90% of the time, because that one time in 10 in which it fails may be the only transaction that matters. But for adventurous folk who typically carry four or five credit cards and a few loyalty cards in their wallet, Coin is a surprisingly effective and practical way to shrink that down to just two.