Forget tablets, forget handhelds, and forget handsets. Wearable PCs may be the next big thing.

Until very recently, Xybernaut, the leading wearable computer company, had about 75,000 individual investors. Suddenly, that's changed. Institutional investors now own 5 percent of Xybernaut shares, and the company has contracts with FedEx, Office Depot, and CSX Transportation. According to Mike Binko, vice president of corporate development at Xybernaut, this is a sure sign that wearable computers are going mainstream.

Although the distinction may be difficult to grasp at first, there are a number of quantifiable differences between a handheld, a notebook, and a wearable PC.

Unlike handhelds, wearables let you look, rather than squint, at their screens. A Xybernaut Atigo has an 8.4in display, versus the 2.25in display on my Palm Tungsten handheld. At the same time, the Atigo weighs just .8l6kg, including battery, compared to 1.3kg for the lightest notebook.

A great deal of the difference, however, centres on the user interface. A wearable allows hands-free operation. It attaches to the user via a belt clip or some other means and offers a variety of alternative input methods. The US Army, for example, equips its helicopter mechanics with Xybernaut units configured with voice technology and even heads-up displays, where necessary.

At one time, CSX train conductors faxed in handwritten work orders at the ends of their shifts, including the next day's configurations of the trains. CSX Technology, the IT arm of CSX, created a mobile, wireless work-order solution to replace the old system.

CSX wanted screens large enough that it wouldn't have to repurpose its data for handhelds, but the conductors didn't want to lug around 2.26kg notebooks, Mike Jenkins, a co-founder and the CTO of Xybernaut, told me. With the new application based on Xybernaut wearables, conductors plug work orders into electronic forms, complete with fields that must be filled in before they can be sent. The result is a far more accurate process that actually lets the conductors get home earlier.

Now add an RFID (radio frequency identification) chip and wearables get even more mainstream, especially for any company that wants to automate data collection.

Midnight Auto Holdings, an auto repair franchise, wants to make getting your car diagnosed and fixed so easy that you'll go to Midnight rather than to your dealer. Every Midnight Auto customer gets a card with an embedded RFID chip. Using a Xybernaut Atigo wearable, a Midnight Auto mechanic can query this chip to call up a customer's history with the company.

Using a wearable, rather than a notebook, also makes it easier for a technician to sit behind the wheel and plug a cable into the diagnostic port behind the driver-side door panel. The wearable gathers what the car's readings should be from a wireless network and compares those to the results it's actually getting. In less than two minutes, the customer is told what's wrong with the car and what it will cost to fix, said Don Futch, vice president of Integrated Business Systems and Services, an RFID infrastructure supplier that partnered with Xybernaut on this solution.

As CSX and others are learning, with wireless technologies such as RFID wrapped around a wearable intelligent device such as the Atigo, mobility can be used to change and improve hundreds of businesses processes.