On Demo Day at Y Combinator this summer, which is technically two days of presentations from graduating companies for potential investors and alumni, Kanishk Parashar didn't have the product his company was creating in hand. He just had an audacious, albeit slightly precarious, idea: Let me combine all of the credit cards in your wallet into one smart, secure, Internet-connected card. 

Parashar assumed he'd sell a just a handful of the pre-ordered devices, which he couldn't promise would be in buyers' hands for roughly a year. He sold 250.

That idea for a universal wallet, in the form of a single piece of plastic slightly narrower than a credit card, with a familiar magnetic stripe, elegant circle logo, and tiny digital screen resembling that on a pocket calculator, is debuting to the public for pre-order today. It's called Coin.

The Coin cards available to the public are still in production, but several prototypes exist. Here's how they work: A Coin owner scans in his or her credit cards to the Coin app, using Square or similar smartphone-payment device. The phone syncs with the card, loading credit-card information onto it (really, any magnetic-strip should work, including loyalty cards or prepaid cards). To pay for a purchase, a user can toggle through viewing the names of her cards by tapping the round Coin logo, and the magnetic strip on the Coin card will switch to that of the respective card. When it's used in place of a credit card, it functions as the selected card, and payment is processed through the user's account, be it American Express, Visa, or a loyalty card. The average credit-card user has 10 cards; with Coin, she can carry just the Coin card, and have access to any of them.

What's most innovative, perhaps, about Coin, is its security features, which land it solidly in the realm of the Internet of Things. It's connected via Bluetooth Low Energy to a user's smartphone, and if that device becomes too far separated from the card (say, you pay at a restaurant and leave the card behind), it sends an alert. If the user doesn't respond, or the card remains separated from the user, it shuts down.

Two Transitions and a Leap

A company lodged so firmly in the hardware space might seem surprising from Parashar, a 33-year-old longtime software engineer whose chops include a stint at PayPal, a gig creating Flickr's mobile functionality, and several jobs developing mobile apps for early-stage start-ups. Before 2008, when he'd taught himself mobile development, Parashar was employed as a Web developer. 

His latest career reinvention, as Parashar tells it, was spurred by a combination of industry forces he was following, and a personal trauma--tearing cartilage in his knee--that resulted in a snap decision.

"While I was recovering from surgery I was on these powerful drugs and feeling great, and I thought, you know, I had this idea back in 2010 and I really want to do it," he says. He had begun to think hardware and devices were taking up some of the Silicon Valley buzz that used to surround the social-local-mobile development space. "And for some reason I wrote an email to my management team and I quit my job."

The following morning was a hazy double-take: "Did I really quit my job yesterday?" Parashar recalls thinking. He spent the next six months learning how to build hardware, by watching tutorials online and taking classes at the membership-based manufacturing studio TechShop in San Francisco. 

By the time his idea for an upstart was accepted into Y Combinator for this summer, Parashar decided to test out his new skills by bringing a product--a totally separate, much simpler product--to market. And this October, he did: It's called BLE Arduino board, which, essentially, is a tiny piece of hardware that allows a chip to be in contact with a smartphone through a low-energy Bluetooth connection. It could be programmed to be a physical sensor that would alert a user of changes around it, or to react to commands from a smartphone. (Currently, lost-and-found applications such as Tile use BLE for this sort of location-aware function.) The goal for the company in releasing a test product was twofold: First, to experiment with a hardware release in order to experience the potential supply-chain, production, and distribution pitfalls firsthand before releasing Coin; second, to give back to the developer community.

"What it does is allow a software developer to become a hardware guy," Parashar says. "It's empowering. When I started, if I'd had that, I would not have wasted about six months learning the hardware." 

Coin, the company, is today a seven-person operation based in San Francisco. It's taken limited outside funding, both from Y Combinator and Palo Alto-based venture capital firm K9 Ventures, which came in as a supporter before Demo Day. The company's impressive roster of talent helps bolster its odds of success. The company's software lead is Russell Taga, former vice president of engineering at HotelTonight. The hardware lead is Karthik Balakrishnan, an aerospace engineer.

Perhaps the secrecy of Coin in general, combined with its early crowdsourced product launch (despite that the Arduino board isn't shipping until December), has contributed to buzz around the new product, which is going on pre-sale through crowdfunding for $100 Thursday. I personally heard glowing whispers of it from two venture capitalists, neither of whom have significant financial stakes in the company, nor seemed to know precise details of how it functions.

Beyond Payments

As boatloads of "smart" Internet-connected devices appear in stores and move into homes, vehicles, and offices around the world, there's a big open question about how humans will effectively engage with them.

Parashar believes the future of Coin might be to take that interactive capability out of the smartphone, and into a simpler device--one that doesn't take photos or store hundreds of apps or need daily charging. One that might look a lot like, or even be, Coin.

"There's a concept that's not on the market right now...and I'm calling it the identity beacon," Parashar says. "Once you opt in, your identity beacon, which could be your Coin, based on other connected devices around you, could help navigate the world for you."

Meaning: the Coin could someday ping the smart lock on your front door to open it as you--and only you--approach. Or it could alert Bloomingdales clerks when a frequent shopper is browsing the racks.

It looks unlikely Parashar will be undergoing another transformation anytime soon. He says CEO life suits him. "I'm having a great time," he says. "It feels like freedom."

Here's Coin's demo video with a simple explanation of its features, and a couple of use-cases: