Children at a special needs school in the Indian capital, New Delhi, are looking forward to Jagdamba Gosain's class. The teacher pulls out several iPads from a bag.

Many of the kids suffer from autism spectrum disorders, cerebral palsy and speech disabilities.

Gosain says Avaz, an app installed on the iPads, is helping the children communicate.

"It helps children who have a problem with speech but who can hear well. They are improving. And if children can have an iPad to themselves, all day, instead of having to share, it will go a very long way," Gosain says.

Avaz uses picture symbols and high-quality voice synthesis to help users create messages and develop language skills.

The speech therapy app was developed by Ajit Narayanan, a visual grammar engine inventor, and his team at Invention Labs.

Revolutionizing speech needs

He says tablets, such as the iPad and android-based devices, are revolutionizing the way children with special needs communicate.

"This product helps children to communicate, using pictures and gestures. When they tap the different pictures, they are sequenced together and the sequence is converted into a sentence, which is then read out," says Narayanan.

The app was developed in collaboration with 25 schools and 500 children - with only one objective in mind. And that was to help children with autism achieve the most effective, interactive communication possible.

It currently offers three graded research-based vocabulary sets, with over 5,000 core and secondary words prearranged into categories. It is available in English and six Indian languages, because of its roots in India.

But more languages are planned.

Speech synthesis is expensive

Narayanan says both Danish and Italian versions are available and more languages are in the pipeline.

"Autistic children and those suffering from hearing disabilities suffer a lot in expressing themselves, although their parents, relatives, and special teachers can understand their expression through body language, eye or hand signs," says Vaidehi Subramani, the executive director of Akshay Prathishtan, a special needs school. "This device has come in handy to address this difficulty."

Speech synthesizers can be very expensive - and, at about 70 euros, Avaz is not cheap.

And Narayanan says he needs a fresh round of funding to develop the app further.

"I have been working on a new technology called Free Speech," says Narayanan. "Free speech is a system where you don't just replace words with pictures, but you replace entire sentences with picture maps."

Autism is not a rare disorder.

It is the third most common developmental disorder, with some studies suggesting about 20 in every 10,000 people will be autistic or have autistic symptoms. The tendency is growing at an annual rate of 10 to 17 percent.

So with yet more language versions in the pipeline, Avaz may well go far to help people wherever they are in the world. But as is so often the case, money is one of the biggest hurdles it faces.