Ever wished you could ring up a friend just by winking, or turn off a light by yawning but without getting out of bed?

Researchers at Nankai University in Tianjin say they have worked out a remote-control gadget that can send simple instructions to cell phones, lights and other modified devices by facial expression.

The gadget, which includes a headphone-like brainwave scanner and a receiver that connects to a laptop, can read the user's mind. Software installed in the laptop then instructs a preselected cell phone to ring, said Duan Feng, associate professor in the university's automation department.

Duan said such control is possible because when people move their muscles they generate a kind of surface signal, recording muscle activity. The signal alters as you change muscle groups, which can help distinguish the part of a muscle being used.

Hao Chao, a graduate student in Duan's laboratory, demonstrated how the gadget works for China Daily, by putting on headphones with several antennas.

His cell phone automatically started calling Duan without him touching it.

Duan, 35, said, "This device is helpful for people who need remote control, such as the elderly, the disabled or those with difficulties speaking."

The price is also affordable, he said, with the major cost being that of the brain scanner, which is about 2,000 yuan ($322).

The method can be applied in other circumstances such as a computer game, which uses the brain scanner as a joystick.

"I'm putting up a so-called smart house as a display room, where the method will be applied to control many similar electronic devices such as a light, air-conditioner and television. Such a smart house will be suitable for the elderly who live alone if this can be put to civilian use," Duan said.

As complex equipment is not required, the cost of refurnishing such a house will be acceptable for ordinary Chinese families, Duan said.

"I always believe that scientific technology should be used for the people, rather than stay in the lab," Duan added.

"China is rapidly aging, and the physical functions of a paralyzed person will be impaired when they are confined to bed for more than six months. Machines designed to help the elderly will be urgently needed soon."

The professor and researchers from Maebashi Institute of Technology in Japan have also built a machine to assist walking.

The machine, which resembles a wheelchair, can analyze the direction of the walker with a force sensor installed in the handle. The sensor can pass on the intended moving direction to a power generator fixed to the wheels.

A video provided by Duan showed a Japanese grandmother who could otherwise walk only three or four meters now able to stroll around the National Rehabilitation Center for Persons with Disabilities in Japan.

Wang Jichen, an employee at a Tianjin nursing home, said many old people cannot walk long because their knees are weak.

According to China's National Committee on Aging, the population aged over 60 will exceed 200 million next year and will comprise more than 30 percent of the population in three decades.

"Empty nest" households, or senior citizens with no children around to relieve their solitude, comprise more than 31 percent of Chinese families, according to the Blue Book of China's Society, published by the Chinese Academy of Social Sciences last year.

Zhang Yi, deputy director of the academy's institute of sociology, said China's elderly population has been rising rapidly in recent years. How to take care of the elderly is a subject that requires an urgent solution, especially in a society where most urban families have only one child, and where many people in rural areas migrate to cities.