Mobile phones, PDAs, laptops, MP3 players, desktops, set-top boxes, portable stereos and digital televisions - the number of digital devices is increasing all the time.

Perhaps we are not getting convergence but divergence - an era of "pervasive computing" where wireless communications and "always-on" connections to the internet provide links between a wide range of devices and appliances. "There are myriad devices coming to market," says David McKenzie, director of pervasive computing at International Business Machines.

Ordinary household appliances, such as air conditioners, will become "smart". IBM recently entered into a partnership with Carrier, the air conditioning and refrigeration company, to build web-enabled air conditioners that can be controlled from a mobile phone or PDA and can automatically fax or e-mail diagnostic information to service staff.

Furniture might also become wired. Accenture, the business consultancy, has developed an "online wardrobe". It keeps a record of the clothes in it, so a consumer, when shopping, can call up pictures of all the items he or she has in the wardrobe and can compare them to the items in the shop.

The online medicine cabinet is another device developed by Accenture. This is able to recognise people and match them with the medicines in it. Warnings are given if a person takes the wrong medicine or the wrong dosage.

Telematics, the transmission of data between systems and devices, will have widespread application, especially in cars. Vehicles will be able to tell how far it can travel on the petrol in its tank and where the nearest petrol stations are located.

Another class of device is the wearable computer, subject of considerable research and development in both the US and Europe.

Det Norske Veritas, the risk management company, is using wearable computers for ship inspections. Each one has a tiny eyepiece that acts as a screen. This facility allows an engineer to call up data and technical drawings on the vessel while the inspection is being carried out.

Other applications are in the inspection of aircraft and use in roadside maintenance, says Mr McKenzie. Further applications may emerge in the banking industry.

Communication

All these different devices will need a way to talk to each other without having to run cables between them.

Wireless networking, using the Bluetooth, HomeRF or the 802.11b standards, will be how these devices communicate over short distances, says Doug Rediker, managing director of TD Capital Communications Partners, part of TD Capital the private equity arm of Toronto Dominion Bank.

Bluetooth is vital, agrees AU-System, the Swedish IT Consultancy, which, to make a point, used Bluetooth to connect a wristwatch to the internet via a mobile phone.

These standards are, however, suitable only for short-range networking. If this multitude of devices is to communicate across cities, countries or the planet then the telecoms operators need to build networks that allow this to happen.

Telecom networks, using the Internet Protocol and given the right software, will be able to transmit any type of data, says Matthew Finnie, senior vice president of products and service at Interoute, the telecoms company, while providing sufficient quality of service. Wireless networks would allow more flexibility, but the mobile internet has not taken off.

"Wap [Wireless access protocol] has not fired the public's imagination," says Mr McKenzie. This does not mean that wireless internet communication will not make a difference, he says.

It will soon be given a fillip by the new faster GPRS mobile networks with speeds, in practice, of about 50 kilobits (thousand bits) per second (Kbps), about the same as connecting through a modern modem, so fast enough for relatively painless internet experiences.

Connection speeds are not the end of the story, though. Pervasive computing will not happen unless reliable "always on" internet connections are available, says Mr McKenzie. "Networks must be like the phone or television networks: on 365 days a year, 24 hours a day," he says.

Then there is the issue of ensuring that the devices can actually communicate in a common language. The challenge, says Mr McKenzie, "is to make the devices transparent to applications and content". This can be achieved by using technology such as IBM's "transcoding" that translates content so it can be used on a variety of devices.

The need to ensure products by various manufacturers can communicate has encouraged many technology companies to commit to open standards. IBM, for example, is putting much emphasis on XML, the extensible markup language that allows content to be described and understood by computers.

It is also promoting the use of Java, the computer language developed by Sun Microsystems. Java is ideal for communication in a networked environment.

Another open technology favoured by IBM is Linux, the open source operating system, which may well become a de facto in the embedded market - it is already used in everything from automobiles to personal video recorders to wristwatches.

Standards, which allow discrete devices to communicate, such as Soap (Simple Object Access Protocol), backed by IBM, Microsoft and Lotus Development Corporation, and XML-RPC (eXtensible Markup Language - Remote Procedure Call) bring the possibility of ubiquitous computing that much closer.

On top of these nuts 'n bolts standards and languages needs to be a "platform" or "middleware" so that the infrastructure looks identical to any device. Microsoft has made efforts in this area with .NET.

For IBM, it is WebSphere, an application server environment on which the interconnectivity can be built.

The infrastructure is ready to be built, but does anyone want to use it?

"Diversity enriches people's lives," says John Mahoney, technical director of Brainstorm, the wireless consultants. He believes that divergence has the edge over convergence because consumers prefer having discrete devices, each doing one thing well, rather than one device that does a lot of tasks badly.