(FORTUNE Magazine) – Will teenyboppers use their cell phones to play games while strolling through the mall? Will salespeople use them to download data from the home office? Will investors use them to trade stocks on the run? Yes, everyone is excited about the potential of wireless Web phones, but no one is quite sure how people will fit them into their lives. To arrive at that answer, software makers around the globe are busy playing a new game called Let's Invent Mobile Internet Killer Apps. Currently hundreds of startups are dreaming up neat services for the mobile Internet.

Want a glimpse of what's become known as "m-commerce" (as opposed to PC-based e-commerce)? Talk to Andreas Stroberg, an amiable 27-year-old networking engineer and the chief technical officer of Wezapp, a Swedish wireless portal. In his Stockholm office Stroberg calls up on his laptop a promotional animation of the company's new WAP (wireless application protocol) cell phone software. Here's "John," walking along a street, where he spots a billboard advertising the latest Volvo. John wants a test drive, so he calls up Wezapp on his mobile phone and relays the digital code number at the foot of the billboard, plus a message setting a time and place. Sure enough, the Volvo turns up on John's doorstep a few hours later.

So far most of the m-commerce ideas being churned out by people like Stroberg don't seem to be connected with the real world. (Why doesn't John simply call his nearest Volvo dealership?) And even if the ideas are good, WAP's slow, clunky delivery has lowered expectations about the mobile Internet's short-term potential. "There's not a lot you can do with such a small screen and a limited user interface," says Katrina Bond, author of a recent report on mobile e-commerce for Analysys, a Cambridge, England, consulting firm.

But in Asia there's one country--or, rather, company--that has moved ahead in this game. Japan's NTT DoCoMo has already built a business, on the basis of a non-WAP mobile Internet service called i-mode, with ten million subscribers. In effect, i-mode is the world's consumer testing laboratory for all the real-time, interactive things you might want to do on the move, from swapping jokes to exchanging photos. Many of these services will spread across the planet once third-generation (3G) wireless technologies allow much larger chunks of data, including video, to be downloaded at greatly enhanced speeds. Says Nigel Deighton, a wireless-industry expert for the Gartner Group in Europe: "Wireless is going to become the preferred business-to-person communications medium, not just for voice but also for data."

It's reasonable to assume that many of the hundreds of mobile startups currently sprouting up around the world won't make it. Either their business model will prove to be flawed or the next big mobile service they're peddling will turn out to be, well, not that big. Who will be left standing once the dust has cleared? Most experts agree that it will be companies that understand that wireless is different from the fixed-line world of the Internet. Tim Devine, a wireless expert at the PA Consulting Group in London, puts it this way: "The term 'mobile Internet' grates on me, because it doesn't capture the richness of all the other services you would want to use wirelessly." The six software startups profiled here are linked by one common theme: They're all run by people who have grasped why mobile is different. That doesn't sound like much, but it's the first, indispensable conceptual leap on the road to hitting the mobile Internet jackpot.

--Richard Tomlinson