Being the thoughts and writings of one Gustaf Erikson; father, homeowner, technologist.
Frank and Russell have pointed out some problems with the user interface (UI) on smartphones. Specifically, the Series 60 OS used in most smartphones today.
For the purpose of this post, I define "smartphone" as a mobile phone that has an OS that can accommodate non-trivial extra applications. Examples of smartphones are the Nokia 6600, Siemens SX1 (Series 60), Sony Ericsson P900 (UIQ), Treo 600 (PalmSource), Orange SPV C500 (MS Mobile). "Phone" on this context is a traditional mobile phone. Examples are Sony Ericsson T610, Nokia 6620, Samsung E700.
Phones have some core applications. Central ones are making and taking calls, handling addresses, and messaging (SMS, email, IM protocols). Cameras probably also fall into this category. Less central areas are Web browsing, calendars, etc.
Ideally, all phone functions should be accessible using the keypad one-handed. This means using the thumb of one hand. The Sony Ericsson smartphones use a jog wheel under the index finger of the dominant hand (the right one). Relying on this feature for accessing functions excludes all those who prefer to use their left hand.
An alternative to shoe-horning everything into "thumb-mode" is a two-tiered approach. Basic functions are accesses using a keypad, but an auxiliary keypad or stylus+touchscreen combo is used for more advanced features. But where to draw the line between basic and advanced?
I have had the misfortune to configure email on both a recent Sony Ericsson and a Nokia. Tapping in multiple server names without the benefit of copy and paste sucks. A PC-based app would help here. Another solution is a web interface that sends a SMS with the configuration.
But this begs the question: why do I have to do this? Why can't I buy a phone where the data connections Just Work? Why is MMS and GPRS settings different? Why do I, as a consumer, have to care about whether my phone manufacturer and my service provider has their act together?
Speech recognition holds some promise, but will remain a complement to the keypad.
How about gestural interfaces? I did a bit of research about applications of gestural interfaces in the course of writing my graduate thesis. (For the morbidly interested, you can download it here). An example is scrolling through an image gallery by tilting the phone from side to side. Another is answering a call simply by picking up the phone. My guess is that inertial interfaces will be on par with speech interfaces; a complement to a primary interface which will still be keyboard + screen.
However, the keypad is often woefully underutilised. Usually there's some buttons that are dedicated to navigation, or a joypad. The large 3x5 grid of numerals are used for inputting numbers and text. How about using the '3' and '9' as PageUp and PageDown buttons when browsing sites?
Who will usher in the Mac Age for mobile phones? Not Apple, they can't cover the mobile space (they outsourced the development of the iPod). Maybe Nokia can rise to the challenge. Another contender is Sony Ericsson, with the Japanese half in charge of making lots of tiny devices easy to handle. Another contender is Microsoft, if they're serious about taking the mobile space to the next level, and not just treat it as an adjunct to the desktop space.