A "half notch" down in terms of profitability are increasingly ubiquitous sales force automation solutions, which in many cases only requires deployment of packaged applications. They give sales people real time access to critical information about product availability, customer history and allow them to gather information using electronic forms on a mobile device, record transactions and transmit data wirelessly back to the office.

"In this day and age if a sales person doesn't have a BlackBerry or something similar, you kind of question their worth," Clark says. "If you're out on the street, those hours and minutes and seconds really matter. It effects the number of calls you can make in a day, the number of deals you can close in a month."

Most mobile applications generate a return on investment by allowing workers to spend more time in the field with customers or more time on business processes and less time at the office or communicating with the office, Dyer says. Business cases for many mobile applications are "pretty straightforward," Clark adds. If it can be shown to increase sales between 8 percent and 10 percent, that increase will easily cover costs of implementation.

Dyer notes that much of the recent investment in mobile applications has been around improving productivity and increasing revenues. But Yankee Group identifies two other business cases: reducing costs - partly a matter of reducing costs of deploying and maintaining mobile applications themselves by integrating them better - and improving customer service.

"Most of the first wave [of deployments] is around increasing revenues and improving productivity," he says. "But I think in the next wave we'll see a lot more applications and services for decreasing costs."

Do mobile applications really deliver the return vendors and analysts claims?

Clark's colleague, Ken Dulaney, vice president of mobile computing at Gartner, is a contrarian on the question. ROI calculations are inconclusive at best, Dulaney says, because companies rarely go back and check to see if the application actually delivered promised benefits.

"These projects mainly get justified on management emotion," he contends. "Which is fueled by competitive pressures. Or sometimes there's just a sheer will to streamline and automate - it's almost a passion in some companies. There's also often a wear-down factor - a project is pitched over and over and finally management says yes."

This is not to say it's impossible to justify mobile applications on more rational grounds. For one thing, , Dulaney says, they're often not terribly expensive because the mobile devices themselves have come down in price so far. Where mobile applications do most good is filling in "missing links" in supply and information chains that are the lifeblood of every business. Not knowing where a truck is between the time it leaves one location and arrives at another is a simple example.

Eliminating those discontinuities "makes the supply chain faster and more efficient and allows companies to cut down on inventory, and that means more profit and a better top line," Dulaney says. "The trouble is, [these applications] don't deliver benefits in real big chunks. It's a lot of small efficiencies that collectively add up."

The ultimate measure of benefit that companies are looking for is a reduction in labor costs, but it's often difficult to draw a direct line between deploying a mobile application and reducing the work force. The benefit may not click in until far down the line.

For all the excitement growing around advanced enterprise mobile applications - or that vendors are trying build -it's still only a tiny part of the total mobile picture. The wireless PDAs and smart phones needed for most of these applications represent only 16 percent of the installed base of mobile handsets today.

"If you look at the killer app for enterprise mobility, it's still voice," Dyer says. "Over time, though, that's going to shift."

Next time: the battle for the corporate palmtop.