As mobile devices evolve and grow more sophisticated, so too do the ways that we interact with them.

As a number of observers have realised, the real innovation in Apple's iPhone was not its touchscreen and soft keypad - they've been around for several years - but its multi-touch capability, where by using two fingers at once, you can easily access extra capabilities such as zooming an image.

The next steps in this revolution are likely to come from the combination of two more technologies: haptic feedback, and capacitive touch sensors. Between them these two will allow devices to have controls that are functionally soft, and therefore reprogrammable, yet feel very solid.

Haptic feedback uses vibration, but unlike your average silent ringer, it is much more controllable in its frequency, duration and intensity.

That might sound like the tactile feedback that gamers now expect from consoles and the like, but it's much more than just games, argues Terry Warmbier, European business development director at haptic specialist Immersion.

"As you go to touchscreen phones, haptics are essential," he says. "Touch is our second most important sense but has all-but disappeared from the physical interface."

Immersion's technology can add feedback, especially into touchscreens, but also into other control devices. For example, as well as being inside several mobile phone models, it is also in BMW's iDrive in-car joystick.

Tricking the brain

In the former, it enables each key of the on-screen keyboard to feel different, and can even use controlled vibration to trick your brain into feeling a key moving under your finger. In the latter, it can add clicks to make a smooth-turning control feel like an old-fashioned mechanical rotary switch - to help the user dial through a menu-list, say.

"You could use keyclicks, but that doesn't tell you which key you pressed. You could use different tones, but touch is how your brain works," says Warmbier.

While vibrating ringers are still moving masses - although they're lighter than they used to be, because phones are thinner - Immersion is now working with piezo-electric technology. This is solid-state, and compact enough to be built into a screen panel.

"We are working with display manufacturers, mostly on larger screen with piezo elements built in for very focused vibration - then you can make it feel like a physical button, or change the feel of a button," Warmbier explains.

Haptic technology is also going into kiosks, ticketing machines, and reconfigurable video games in Las Vegas, he says. In addition, Samsung now has a phone out - though only for the South Korean market so far - with 22 different types of vibration, including clicks on the radio volume 'knob' and typing noises in text messaging.

Warmbier adds that the ideal from a usability standpoint appears to be a combination of colour change, sound and haptics.

Sensing a touch

In mobile phones and other devices, haptic feedback is being allied to technologies such as capacitive touch sensing. This is the same thing that's used in many laptop touchpads, but it has now been applied in transparent form to touchscreens, and also under curved plastic surfaces.

The latter means that it can be used to add controls to a device, says Robyn Palmer, a marketing specialist at capacitive sensor developer Synaptics.

For example, a mobile phone control-key now need only be an area of the case with a touch sensor, plus haptics to make it feel like a button. Even better, you can add an LED array underneath and use it as a reconfigurable label for the button.

Last but not least, other technologies are adding intelligence to the process. For example, the company that now owns the T9 predictive text system, Nuance, is developing an extended version called XT9 which could help us type on touchscreens.

This not only predicts based on what you've already typed, says William Clement, the Nuance staffer in charge of marketing T9 in Europe, but it can also predict based on what you might have typed.

"With soft-keypads or on modified keypad layouts, people often hit the wrong key," he says. XT9 deals with that by widening its pattern-matching to include the possibility that you hit the wrong key, missed a key, or hit the right key once too often.

Of course, the specific errors that you can make will depend heavily on the layout of the keypad and will differ from device to device, Clement adds, so XT9 will need specific rules for each device or layout.

Still, it's not that long ago that the idea of using something the size of a mobile phone for tasks that you'd normally use a laptop for was laughable. Now, thanks to new user interface technologies such as these, the device manufacturers can talk of pocket computers - and nobody is laughing anymore.