The remarkable dexterity of the human tongue has been harnessed by medical engineers to help the severely disabled. They hope that patients who cannot control their head or limb movements enough to take advantage of new technologies may still be able to use simple tongue movements.

Researchers have built a small electronic device which can be embedded in a dental palate. Once inserted it can be switched on and off with the tongue, triggering a current in a coil of wire around the neck and setting off a host of events.

The device was revealed at the Royal Society's "New Frontiers in Science" exhibition this week.

"The tongue is an extraordinarily accurate sensing device and motor device," said Robin Luff, consultant in rehabilitation medicine at Kings Health Care NHS Trust. "And when nothing else can be moved the tongue can still be moved."

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These facts led oral surgeon Colin Parker, now retired, to suggest several years ago that microelectronics could be embedded in a palate. When the patient - someone with severe motor neuron disease, for example - touches it with his or her tongue it sends a radio signal to a coil of wire around the neck, which triggers an electrical signal.

The signal can control anything, says Luff. Wires from the coil can go to an electronics box on the side of the wheelchair which can send infrared signals to a computer. There is software that can be operated by "switch access" - only receiving the signals "on" and "off".

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Donna Cowan, research fellow at the department of medical engineering and physics at Kings College London, said that patients with restricted hand movement can operate this software more quickly with their tongues than their hands. "You just have to raise your tongue and exert pressure on the roof of the mouth," she said.

The device has yet to undergo a full clinical trial so it will not be available for some time. Ultimately, said Dr Luff, a palate could contain several switches. A patient could then control a wheelchair along two dimensions instantaneously.