Barbara Ballard defines a device classification scheme based on user needs and behaviors in A New Device Taxonomy. I welcome this approach as I also consider the old classification smart phone, PDA, mobile phone as absolutely irrelevant.

• General purpose work devices, currently dominated by desktop computers, tablets, laptops, and the like. These devices can do a wide variety of information-centered tasks. Contrast these with special-purpose work devices, such as the UPS Diad delivery driver device. Users are likely to have a general purpose work device available or carried while working, but not while outside of work hours.
• General purpose entertainment devices, such as the iPod video and Sony Playstation Portable. These devices might be game-centric, book-centric, or media-centric, but are intended to readily support the use of other entertainment media. They may even have communications service.
• Communications and control devices, which include phones, desktop phones, PDA, Blackberries, and a plethora of future devices. These devices that allow the user to communicate with others via voice, text, and other methods.
• Specialized devices, or information appliances. These include watches, iPods, ATMs, GameBoys, and so forth. These devices are focused on delivering a specific experience to the user, and if they do other things, those secondary items are very secondary. An iPod has a calendar on it, but it in no way interferes with the use of the device as a music player.

But I think even these categories - especially work, entertainment, communication - will more and more be intertwined. Right now these categories make still sense, but not for long. Even today police officers play GTA with PSPs to learn to drive better with their real cars. Is this work or entertainment?

She continues with the Personal Communications Device (PCD) from the communication and control category. I find the examples she gives very interesting. Then she creates new categories like voice-centric, messaging-centric and information-centric:

A PCD is always carried, and is thus described by The Carry Principle. It is multi-purpose, but will be configured to market segments’ needs. Like some drivers need small efficient cars and others need large trucks for farm work, some PCD users need a messaging-centric device and others need a voice-centric device. Still others, such as doctors, may actually need an information-centric device.

Couldn't it be that we use devices according to our own personal characteristics. Some people like to watch, others to read and still others to listen and they will most often choose and/or use a device accordingly - regardless of such categories as work, entertainment or communication.