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.