The $500 Luminae keyboard works thanks to "frustrated total internal reflection." In other words, cameras underneath the curved glass pick up on when your fingertips interrupt the light patterns in the keyboard.
The Luminae started life as a vaporware Kickstarter project that tripled its funding by the time it closed in January 2012. A year later, creator Jason Giddings holds an actual keyboard on display at CES 2013.
Each Luminae keyboard has three cameras that sit below the glass, looking up. The curved see-through design gives it a futuristic look. The keyboard overlay is completely customizable and can be removed and replaced when desired. Luminae expects to be shipping to customers in about three months, giving the developers time to work out some kinks in the software.