The arrival of the desktop PC ignited a revolution not only in information technology, but also in information expectation. As companies steered away from dedicated data processing departments and opened up their databases directly to managers and employees, so the expectation of real-time access to corporate data increased.

That trend means that PDAs (personal digital assistants) with wireless network access are now becoming de rigueur among corporate executives. But for some people – and some professions – who need constant, easy access to data, not necessarily from the corporate database, wearable computers are becoming both a viable and more attractive proposition.

The Massachusetts Institute of Technology defines a wearable computer as anything that is always with the user and is as unobtrusive and as comfortable as clothing. They are generally operational when the user is moving; can be used without hands through voice-recognition technology; have sensors to detect the environment; deliver messages as soon as they receive them; and are always on.

The Giga Information Group predicts wearable computers will become as common as today's PDAs within 10 years, while Gartner predicts 40% of adults will be using some form of wearable computer by the end of the decade. That kind of potential has spurred a number of companies to start working on wearable computer designs (see box).

In contrast to PDAs, however, the first to embrace wearable computers will not be company executives but workers. Today, most wearable computers require users to strap CPUs (central processing units) to their belts and wear head-mounted display units with microphones, earphones and a see-through miniature display. Manufacturers acknowledge that office workers are unlikely to suffer such demands, so they are instead aiming their products at people who are constantly moving around and have no time to go back to a computer for information.

Aircraft-manufacturer Boeing has developed a wearable computer for aeroplane maintenance operations. Workers can crawl under and through aircraft, testing and repairing components, using the computer to access up-to-date information and diagrams from manuals, order replacement parts and email any problems immediately to co-workers. Since technicians are already accustomed to carrying equipment either in hand or strapped to the body, they usually accept the inconvenience of the computers as a reasonable trade-off.

Similarly, warehouse managers can use wearable computers to give them constant access to records, while doctors and nurses can access patient records while they are on their rounds. And in a few months, security personnel at certain US airports will be fitted with wearable computers so that photos and descriptions of individuals identified as potential risks using face recognition technology can be sent to them for instant access.

"Wearable computing will start to play a key role in cost cutting and increasing productivity for many industrial users in the next two to seven years," says Christine Arrington, programme manager for IDC's Emerging Technology Markets group. The use of wearable computers in these real-life situations will also help hone design standards.

Today, typical wearable computers weigh approximately one kilogram, have a mid-range Intel processor running Windows, use some kind of voice-recognition technology for interaction, and have a relatively small hard drive. The big problems that systems manufacturers are struggling with are the size of the systems and the batteries required to power them – the typical battery pack offers only four hours of power.

To help solve the power problem, MIT's Media Laboratory is working on a generator that wearers can put in their shoes to generate power from foot movements. Burnsville, MN-based ViA, which produces a system for warehouse managers, is working with chip manufacturer Transmeta to use its low-power Intel-compatible chips in its designs.

Boeing, meanwhile, is using 'stacked chips' from California-based Irvine Sensors Corporation to reduce the size of its computers. It puts the chips into stacks of 50 to create centimetre-sized cubes that take up less power and generate less heat. Nevertheless, purpose-built chips are still lagging behind their desktop counterparts in terms of power and application support.

Another problem is the size of the screens. The Windows' icon-based interface can be distracting on heads-up-displays and displays based around eye pieces and pairs of glasses. Alternatives to Windows, such as the WearComp Operating System, may be more suited but, as yet, they lack applications.

"The applications to drive consumer interest are several years away and fear of the 'geek' factor will be a huge obstacle for some time, meaning that wearable computing is a commercial application for the next few years," says Arrington of IDC.