It has been two years since Apple launched the iPad and spawned rival tablets from the likes of Samsung, Amazon.com, Sony and now Google and Microsoft.

Much of the competition so far has centred on making smartphones and tablets lighter, slimmer, faster and longer-running, and the trend shows no signs of slowing. But the increasingly crowded marketplace is also galvanising hardware designers and software engineers to explore new technologies.

"We should think beyond just the touch-screen device," said Lin Zhong, a professor at Rice University in the US who does research on mobile systems. "Why do we have to hold tablets, carry many displays? We should think about wearable computers."

Some researchers are experimenting with wearable devices, such as Google Glass, a stamp-sized electronic screen mounted on eyeglass frames to record video, access e-mail and surf the web.

Others, like Microsoft, are investigating the use of 3D cameras to create images that pop up when a person calls. Samsung has a concept video that shows a bendable, transparent 3D smartphone-hybrid tablet that can also be used as a real-time interpreter.

Few of these new technologies will hit store shelves any time soon - companies and researchers are more actively working on touchscreen innovations in the near term. In particular, organic-light-emitting diodes, or OLED, is widely touted as the successor to liquid crystal displays.

The technology could one day allow tablets to be folded or rolled up like a newspaper. Reaching that point poses challenges like making the delicate chips and components inside them more flexible and resistant to damage.

"Flexible and foldable displays will first be implemented on smaller sizes like smartphones," said Rhoda Alexander, IHS iSuppli's tablet analyst. "Tablets may follow in a later progression, once manufacturing costs and yields have been tested."

Manufacturers are also working to improve gesture recognition, augmented reality and voice controls like Apple's Siri.

IBM fellow Bernie Meyerson envisions people having real, spoken conversations with their devices.

"You hand it to your grandmother and it just works. It will adapt, tune itself to your voice," Meyerson said. "You'll have something that you carry around in your pocket and it listens to you when you want it to."