Mobile handsets will have virtual buttons, which will put "haptic" force-feedback technology, often seen in video games, to more serious use.

The technology is already in use for Sony's PlayStation 2 and Microsoft's XBox, where users are familiar with tactile reactions from joysticks and steering wheels. Built into a PDA or smartphone, a haptic screen doesn't actually flex against a user's finger; instead, a small electric motor behind it delivers a small tap. Combined with an audible 'click' feature, the overall effect helps mimic a mechanical button on a digital screen.

Immersion, a maker of haptic technology, plans to license the technology to manufacturers of smartphones and PDAs who want to improve the utility of their touchscreens, said Mark Belinsky, vice-president of market strategy at the California company.

The company already sells a system which mobile phone vendors use to synchronise tactile vibrations with ring tones and games so, for instance, users of Samsung's SCH-A930 mobile phone can identify callers without taking a muted phone out of their pockets, since the phone vibrates differently for each assigned ringtone, Belinsky said.

Samsung also uses haptic technology to add a sensory dimension to video games. Game makers including Punch Entertainment, SkyZone and Sonic Branding Solutions have signed agreements with Immersion to use VibeTonz technology.

Vibrating songs and games are decent gimmicks for selling phones to kids, but the real payoff will come when vendors use haptic technology in their touchscreens, said Avi Greengart, principal analyst for mobile devices with Current Analysis.

"If you're just trying to make a phone that's more exciting for young people, maybe that's exciting or maybe not," he said. "But when it comes to giving force feedback to a handset, this gives you the physical sensation that you just pushed a button, and that's compelling."

As handsets get thinner and begin to host richer media, their designs feature "all screen and no buttons", Greengart said. The challenge for vendors is how to let users know which button to press, and which button they have just pressed. Tactile feedback is the best answer yet, he said.

Immersion has licensed similar technology for years to manufacturers of video game consoles, medical training simulators and automotive dashboard manufacturers. The company is locked in a trademark infringement lawsuit with Sony, which allegedly uses Immersion's technology in the PlayStation series.