Researchers at Germany's Hasso-Plattner Institute have developed what they call imaginary interfaces that allow users to interact with their phones even though they're not in front of them.

The technology uses depth sensing cameras mounted above the users to locate where their fingers are and what they're touching.

Patrick Baudisch' Researcher, Hasso-Plattner Institute: "There were times that we had PDAs and a stylus and company in Cupertino said this is a bad idea. Why would you retrieve the device and the stylus. Let's get rid of the stylus. And that sounded like a really good idea. We say this is a good idea but we want to see this go further.

"Why don't we leave this out and retrieve no devices at all and for these tiny interactions such as turning off an alarm or picking up a phone call or sending to voicebox or setting a timer or something like this people will interact directly on the palm of their hand."

Baudisch said the system could work because users can remember about 70 to 80 percent of their 20 home screen icons and where they're located. Some hurdles for the technology are making the depth sensing camera smaller and more portable, but also training users to use a device they can't see.