Imagine a world where a user’s computer can “talk” to the mobile phone, which can talk to the washing machine, which can talk to a camera, which can talk to a pen, which can talk to the stapler, which can talk to the shower controls… and they can all talk to each other, synchronize, coordinate and download information painlessly and wirelessly — while the user sips a mocha and watches Seinfeld reruns.

Imagine a driver strolling along while the condition of the tires is monitored, mechanical problems are diagnosed, the driver’s passenger sends a fax or plays video games, or communicates with his or her home to turn the air conditioning on.

Sounds like a world of fiction? That depends who’s writing the book.

About three years ago, the tech media had some exciting news: All this and more would be possible in the near future, thanks to a technology named after a Viking king, Bluetooth.

Bluetooth uses the radio frequency spectrum to transmit data, without cables, within a short range, while also providing a common “language” for a variety of devices.

Shortly after the launch, analysts predicted the technology would become a $5.3 billion industry by 2005. Two years later, the same analysts said by 2007 potential revenues would reach $2.54 billion.

Why the sudden plunge in expectations? Especially when a couple of thousand companies were throwing big money into the development pot?

“Bluetooth has been the little engine that could for the last seven years,” says Stephen Wellman, editor of FierceWireless, a daily newsletter covering the wireless industry. “Researchers have predicted the proliferation of technology….but it hasn’t found any popular applications.”

Some Bluetooth applications are successful, especially in the mobile phone market. Of course it helps that Bluetooth was the birth child of wireless-phone industry leaders Nokia and Ericsson. Other adoptions followed. A Denmark zoo uses it for “BodyTags” to help parents track their children’s whereabouts via a wireless phone. BMW has integrated it into a vehicle’s system so a driver can make a call with the push of a button on the wheel. Coca-Cola Amatil armed some sales agents with Bluetooth notebooks to place orders. The city of Oslo uses it to monitor equipment at its water-pumping stations. And GameBoy has promised to launch a Bluetooth module that would allow players to connect to the Internet—just in time for this year’s Christmas.

Forrester research group even said recently that Bluetooth will dominate by 2008, while its highly popular cousin Wi-Fi, or 802.11, is heading for a crash landing.

But despite the exciting current uses, and the even more exciting future possibilities, some teckies and analysts say the technology just doesn’t have enough teeth.

“Bluetooth isn’t dead but it sure hasn’t met market expectations,” says Nelson Ludlow, CEO of Port Townsend-based Mobilisa, which specializes in engineering, research and development of wireless technology. “It’s not as widely used (as other wireless technologies) and people are slow to adopt it.”

Not that companies with high stakes in Bluetooth have been on vacation. The Bluetooth Special Interest Group touts promoters such as 3Com, Intel, IBM, Microsoft and Toshiba, with many of them working together to find and implement new applications. But they seem to have missed the wireless high-tech parade, arriving only in time to watch others like Wi-Fi briskly marching away toward the mass market.

“Popular applications are developed from the bottom up; it’s the geeks that proliferate technology,” Wellman says. “They are impressed (with Bluetooth) but they are not seeing it taking off.”

Nelson said of the many wireless projects his company has implemented only one used Bluetooth. It works well, he says, but there aren’t very many applications that make sense or cannot be done using alternatives. “Why would I want my pen to be wireless?” he says. “It’s great for a personal area network, but do I really need my pen talking to my stapler and so on?” Besides, Radio Frequency Identification (RFID), he says, is the new kid on the wireless block that will do what Bluetooth promises and more in the near future.

Wellman thinks Bluetooth still may have a chance but he doesn’t see the pulse. Some analysts say some of the demise can be attributed to initial hype, but that the promises can still be delivered, with time.

Ironically, Bluetooth’s namesake, Danish Viking King Harald Bluetooth, was said to have enjoyed talking more than conquering.