Forget slide-out keyboards and even fancy touchscreens - the latest data entry interface is air itself.

Engineering students at Duke University in North Carolina have created an application called PhonePen that allows users to write short notes in the air with their mobile phone.

The application uses the accelerometer found in many new mobile phones (the team used a Nokia N95), and can capture letters, numbers and diagram scrawled in the air.

Writing out loud

"We're trying to get past the whole idea of typing on a keyboard or using a stylus to enter information into devices," says Romit Roy Choudhury, assistant professor of electrical and computer engineering.

"Many people get discouraged with current phones and their small keys. As phones get smaller, this frustration will only grow. In the age of Twitter and micro-blogs, the speed at which you send information becomes more important."

The researchers think the application will be used by people creating short notes on the move - such as scrawling their car park bay for future reference. "Also, say you're in a class and there is an interesting slide on the screen," says graduate student Ionut Constandache. "We foresee being able to take a photo of the slide and write a quick note on it for future reference. The potential uses are practically limitless."

Currently, air-writers must pause briefly between letters, which can slow the process down and rules out the use of joined-up writing. Also, each letter must be written large. These improvements would come as a result of improved algorithms and more sophisticated accelerometers, the scientists said.

Roy Choudhury expects that the PhonePoint Pen prototype will be available for download within the next few months.