Do you own a smartphone? Flip it over. What do you see? Maybe there's a hole for a camera, a company logo, and some FCC disclaimers? Do you see the cool design of a case you bought for it? Either way, it's essentially inert. But for Greg Moon and Yashar Behzadi, it was an opportunity to do some clever design.

"We both like strong imagery, and we were running with the idea of electronic, persistent visual personalization in a physical object," says Moon, and the pair had been throwing around ideas for what that could be. "We were walking back from lunch, musing, 'Where is there a big, flat piece of real estate that we could visually configure?'"

Behzadi first realized the answer: the back of a phone. From there, they created popSLATE, a case for the iPhone 5 with an e-ink screen. The innovative device is being launched on Indiegogo today.

The e-ink screen that popSLATE uses is the next generation of screens that are at the core of e-readers like Amazon's Kindle or the Kobo. Like all e-ink screens, it only consumes power when the display is changed. This allows for an always-on ambient visual interface.

What can you do with a second screen on the back of your phone? A lot, it turns out.

The most basic application is personalization. You can put pictures there and other people can look at them. This is where Moon and Behzadi started, and they say that in early user testing people showed a lot of enthusiasm for the ability to change the look of their phone on a whim. But during these exchanges, people would volunteer ideas and feature requests that dramatically expanded their thinking.

"Our thinking really blew up when we realized that it was much more than a picture platform — that 'always on,' in fact, represents a totally novel smartphone use model," he says.

The next level beyond putting your own pictures on the back of the phone is putting someone else's there, and popSLATE includes a photo-sharing back end to enable that. From there, it's a short leap to displaying notifications, maps, to-do lists, speaking notes, and anything else you can imagine that would benefit from an ambient or glance-able display.

Any app you can imaging that benefits from a glance-able display, can make use of the popSLATe… Once the API is finished. Image: Courtesy popSLATE

Here's why this is cool: To conserve battery life, normal phone displays have to turn themselves off when they aren't in use. Phones don't know if you're looking at them, so they guess by using interaction as a proxy for attention. That's fine for interaction modes where we are deeply engaged and swiping and tapping to our heart's content. It's less good for situations where we want to prop the phone up and glance at it from time to time.

Typically, when a notification arrives, your phone chimes, lights up the screen, and then disappears until you physically turn on the device. When you're reading something, if you take too long to turn the page, the phone might decide that you're gone and turn itself off. Thanks to the e-ink display, the popSLATE allows for the opposite interaction. It'll sit there patiently displaying the same screen until the end of time, unless you tell it otherwise. If you're doing something where you want keep glancing at your screen without having to touch anything, like cooking, doing exercises, or glancing at driving directions, this is amazing.

These functions are part of what make e-readers so effective and popular. But what's clever about the popSLATE is that you get the simple benefits without adding another gadget to your life. By attaching itself to the iPhone it skips over the question of fighting for a place in your pockets by becoming part of something you're already carrying. It acts as a symbiote, piggybacking on the iPhone's capabilities.

The piggybacking that popSLATE does runs deep in the product, says Behzadi. Through the iPhone's Lightning connector, it borrows power to change the screen, as well as enable all of the sensors and connectivity that the device has. One of the most clever tricks is how they detect taps on the back.

popSLATE has no sensors of its own. Instead, they use the iPhone's accelerometer. When the phone is face down and the accelerometer detects movement, their app interprets that as a tap. "You rarely have the phone on the back side so we are uniquely positioned to take advantage of that," says Behzadi.

"We're also borrowing from what people already do," he says, "We're taking advantage of a well-established base of users and functionality."

"People often have two social worlds," says Moon. "There's the brick-and-mortar social world and virtual social world. By piggybacking you traverse both of those. On the front of the phone you are sharing virtually. On the back side, you are taking it into the real world, where people can see it and talk about it."

The team is looking to continue to take advantage by offering an API for other app developers to hook into, so they can display myriad things on the back screen. As an example, Moon imagines the popSLATE could support a reading app that displays text on the e-ink display in bright sunlight and on the iPhone's regular display at night. (Are you listening, Marco Arment?)

"I personally like learning people's stories, and I enjoy communicating ideas, so new vehicles for self-expression are always intriguing," says Moon. Image: Courtesy popSLATE

Moon and Behzadi are dedicated to testing out their ideas in the world. Long before the technical design was completed, they created a mock-up. "We used a $2 clear phone case, some tape, and a collection of black-and-white laser prints amateurishly cut to size with scissors," says Moon.

With the prototypes in hand, they could pester family and friends for advice and feedback. "After exhausting friends and family, we chased target users around Starbucks, Whole Foods, my kids' sporting events, wherever," says Moon. This approach perhaps reached its peak when the pair found themselves being escorted out of a mall by security who didn't like the way they were approaching people with clipboard in front of an Apple Store. "By the time we reached the parking lot, we'd asked the guy escorting us what he thought about it," says Behzadi, "He thought it would be pretty cool."

"Sometimes we'd use a subtle approach, simply setting the mocked-up case in plain sight," says Moon, "People would take notice and spontaneously ask questions."

Moon describes this kind of user research as ethnography. "It was sort of ethnography for ourselves too," he says, "Knowing you can change the image at will makes an image feel stale pretty fast."

Once they'd done enough early testing that they were convinced that they had something good in their hands, they approached E Ink to discuss a partnership. Their timing couldn't have been better.

"We went to them with the idea, and they happened to be developing something amenable to exposed use on the phone," says Moon. The screens are laminated in Gorilla Glass and will withstand the same shoddy treatment that the front of your phone gets. Moon thinks that this next generation of e-ink screens is partially a response to a declining e-reader market in the face of low-end tablet sales, as E Ink looks for new places where their product can thrive. He suspects that they're looking to partner with handset makers and integrate the screen directly into future devices. In the meantime, popSLATE will act as a showcase of the possibilities.

popSLATE has angel investors and their IndieGoGo goal is a relatively modest $150,000. Moon says that the launch is more about an opportunity to to get input from an even wider audience of potential users. He sees it as another step in a process begun with their $2 transparent cases and laser-printed mock-ups.

He says it's part of a larger spirit of sharing that he sees sweeping Silicon valley.

"Even a few years ago, it seemed unheard of to throw ideas out to the world very early in the process," he says, "Now it's very viable and takes advantage of the best in the community to quickly develop products that the people will love."

PopSLATE's interface will allows you to choose content for the back screen, whether it's a photo you took, or from a gallery of preset images and things your friends send you. Image: Courtesy popSLATE

All images courtesy of Greg Moon.