You see them everywhere: Annoying people with Bluetooth earpieces permanently mounted on their ears, whether they're talking on the phone or not.
Those earpieces replicate some of the phone's functionality - namely speaker and microphone, plus electronics for muting, connecting wirelessly and other functions. Nearby, a pocket-size mobile phone houses the rest of the electronics, plus hardware and software for surfing the internet, playing music and videos, taking pictures and other functions.
Meanwhile, the biggest challenges for handset makers revolve around conflicting priorities: How do you make the phone as small as possible, but the screen as large as possible? How do you pack a full-size keyboard onto a tiny mobile phone?
The solution to these conundrums is to move or replicate all mobile phone electronics to the earpiece.
The reason mobile phones are the Mother of All Convergence Devices is that the phone part is absolutely indispensable. People must be able to make or receive calls while jogging, working, lying on the beach - everywhere. The only way to make, say, a camera accessible at all times is to build it into the mobile phone, and the same is true for media playing, GPS functionality and other features. The phone must go with you everywhere, and the rest of the functions are just along for the ride.
Imagine being able to leave your full-featured, pocket-size mobile phone behind if you choose, and carry only the earpiece from which you could at minimum make and receive phone calls.
The benefit is that pocket phones could be bigger - bigger screens, better cameras and more electronics - without compromising mobility when you really need it.
Three recent trends make this possible and desirable: Shrinking mobile phone electronics, advances in voice recognition and embedded electronics everywhere.
1. Shrinking mobile phone electronics
The first time I saw a mobile phone in the 1980s, it (combined with the battery) was the size of a brick - and about as heavy, too. Since then, mobiles have largely obeyed Moore's Law, becoming smaller and cheaper and acquiring ever more features all the while.
Obscure handset makers have already designed, built, manufactured and sold complete mobile phones small enough to fit in an ear-wearable size. Trouble is, they're configured like bigger, traditional mobile phones, not earpieces.
For example, there’s a Chinese mobile phone called the Xun Chi 138 that's 2.64in long and weighs 2 ounces. Despite its size, the phone has a touchscreen for text input.
Haier America launched last year its Elegance mobile phone, which is about the size of two fingers - 3.5in long.
Also last year, KTF Korea unveiled its mini EV-K130 mobile phone, which is about the same size as the Elegance.
Australia's SMS Technology has managed to squeeze an entire mobile phone onto a fairly standard-size wristwatch called the M500.
We have the technology to squeeze a mobile phone into an earpiece.
2. Advances in voice recognition
The biggest challenge with ear-based mobile phones is doing away with keypads. The solution is voice control.
Mobile phones that let you dial phone numbers by saying something like "Call Mum" are common. But in the past two years, start-ups have made incredible advances in the ability of a mobile phone user to replace other kinds of button pushing with voice commands.
A company called Vlingo makes an application now in beta that lets you send text messages, get directions and do other powerful things, all by speaking in your natural voice. You can search for businesses on the internet, then dial the number using only voice commands.
Another company, called Jott, enables you to send email using only your voice.
Big companies are getting into the act, too. Google offers its free "Goog-411" service in the US, where anyone can call 1-800-GOOG-411 and run Google searches, all by voice.
And, of course, Apple may be working on mobile phone voice commands if a recent patent called an 'Audio User Interface For Computing Devices' ever bears fruit.
The earpiece mobile phone would need only one button for answering and hanging up calls, and the ability to recognise commands like 'Call Steve Wilson at work'. It would also need to recognise and connect with your pocket mobile phone - and other devices.
We have the technology to build voice-controlled phones without buttons.
3. Embedded electronics everywhere
Mobile phones aren't the only objects in our lives that entertain, inform, organise and enable communications. So do our PCs, home entertainment systems and, increasingly, our cars.
And all of these devices can communicate with phones via Bluetooth or Wi-Fi, if they don't already.
There's absolutely no reason why your earpiece phone couldn't communicate with these devices just like it does with your pocket phone.
For example, you should be able to call Goog-411 and ask for directions, and have them show up with the map on the car's on-screen dashboard - all hands free and without your pocket phone.
The non-phone parts of your mobile phone should be optional, because much of that functionality is already duplicated elsewhere.
We have the technology to connect earpiece phones to multiple devices.
A vision of the ideal mobile phone
Here's one idea about how the ultimate phone of the future would look and function.
Imagine an iPhone with a bigger screen than the current model with a Bluetooth headset-like phone. The pocket phone could make calls without the earpiece phone, and the earpiece phone could make calls without the pocket phone.
The camera electronics would mimic those in the new Sony Cyber-shot DSC-T200, a 8.1Mp camera with a 5x Carl Zeiss optical lens and optimised for high-definition display. Compromising camera quality in mobile phones is no longer necessary.
It would have built-in GPS, gigabytes of storage, and great video and music playback capability. It could connect to the internet over a 3G phone line or via Wi-Fi.
The phone would come with a near-full-size fold-up wireless keyboard, so you could prop up the pocket phone and use it as a Wi-Fi connected laptop, all the while taking calls on the mobile phone in your ear.
We clearly have all the technology we need to move mobile phones one step up the evolutionary ladder. The key is to free the mobile phone itself from its prison inside our radically converged smartphone gadgets.
All we need is a handset maker with the vision to implement it.
Those annoying people with the always-mounted wireless earpieces? They are the future.