It seems like everyone is building a smart watch lately. Pebble ran a wildly successful Kickstarter campaign earlier this year for its e-paper watch; Samsung has confirmed it is making one; and both Apple and Microsoft are thought to be developing their own versions, too (see “Smart Watches”).

One thing that hasn’t been sorted out is how to input text on such tiny screens—gadgets revealed thus far tend to focus on viewing information like incoming e-mails, and allow users to perform simple tasks, like controlling a music player. Without making it easy for users to both receive and send information, it may be hard for smart watches to take off as smartphones and tablets have.

A group of researchers at Carnegie Mellon University has a potential solution for the text-input part of this equation. Called Zoomboard, it’s a penny-sized touch-screen QWERTY keyboard that magnifies a small segment of keys when a user taps it, making accurate typing easier on itty-bitty screens. A paper explaining Zoomboard and a text-entry experiment the group ran to test its utility will be presented at the Computer Human Interaction conference in Paris next week, and an online demo lets you try it out on an iPad.

As paper coauthor Chris Harrison explains, Zoomboard isn’t complicated technologically: it’s just zooming in to make tiny buttons big enough for comparatively fat fingers to press.

When you press down on part of the Zoomboard keyboard, it zooms in to show just the keys in the area you touched. Pressing again types a letter on the screen. In addition to a built-in space bar on Zoomboard’s keyboard, you can swipe to the right to insert a space or to the left to delete. Swiping upward reveals symbols. The keyboard could be scaled as small as a penny for use on smart watches and other small displays, or potentially, scaled up for those who have trouble typing on existing smartphone or tablet keyboards.

“We think it’s really valuable—even if it’s a rudimentary text input mechanism—to have something you can fall back on,” Harrison says.

Using Zoomboard isn’t particularly fast. Harrison and his colleagues had six CMU students try out Zoomboard on an iPad, where the keyboard measured 16 millimeters by six millimeters. After getting some time to play with it, they were asked to type out test sentences. The students were able to enter 9.3 words per minute—quite slow, but with about the same accuracy as if they were using a traditional keyboard.

“The first time they used it, people were actually pretty good,” Harrison says.

Harrison says the group doesn’t plan to commercialize Zoomboard, but he says the source code—which is only about 100 lines—is available online for anyone to use.