Google is working on an Android add-on that will make the mobile phone operating system much easier for blind people to use.

T V Raman, a Google researcher who has been blind since the age of 14, is working on a system whereby touching the screen would assign that point to the number five, the centre of the numeric pad.

This would allow much easier touch dialling for sightless users who could use the whole screen. They would also be able to shake the device to wipe the number and redial.

"The thing I am most interested in is all of the stuff moving to the mobile world, because it is a big life-changer," Raman told The New York Times.

There are already screen readers for mobile phones, but they can cost as much as the handset itself. Raman wants to build in support for the visually impaired right from the start of the design process.

"If I can get another 10 engineers motivated to work on accessibility, it is a huge win," he said.

Raman is also working on a system that would use the phone's mapping software and GPS to allow the sightless user to navigate using spoken directions from the phone. The same system could also help sighted users.

"If you have the technology that can recognise a street sign as you drive by it, that is helpful for everyone," he said. "In a foreign country, it will translate it."