SAN FRANCISCO (CNNMoney.com) - Apple's cavernous booth at San Francisco's Macworld Expo contains snazzy new computers, software galore -- but no iPods.

The rest of the show floor is another story.

Mercedes-Benz was one of the first automakers to offer iPod integration.

iLevel's iWoofer speaker system

Metal iPod Shuffle cases

Apple's (Research) raging iPod sales have spawned an industry unto themselves, which Business 2.0 Magazine dubbed "the iPod economy."

Apple president and CEO Steve Jobs announced Tuesday that during the December quarter, Apple sold 14 million iPods. That's almost 25 percent more than what Wall Street analysts had anticipated.

The iPod economy comprises three main product types: speakers, FM transmitters that allow users to listen to their iPods in cars over FM airwaves, and carrying cases.

Plenty of all three are on display at the Macworld Expo, with a ubiquitous "Made for iPod" sign hanging in numerous booths. Of the show's 350 exhibitors, roughly 20 percent to 30 percent are hawking iPod accessories, estimates Mike Sponseller, public relations manager for IDG World Expo, which puts on the conference.

Gavin Downey, director of product management for Belkin, which makes numerous iPod-related accessories, said the market for such items reached $700 million in 2005 and could climb to $1.5 billion this year.

A quick tour of the Macworld Expo show floor revealed numerous gadgets from companies like iLevel, which showed off its iWoofer, a cylindrical, ultra-mod iPod dock with a built-in subwoofer speaker system and FM radio with auto scan tuning.

It also included companies like Lifepod, a Brooklyn-based maker of whimsical iPod and Mac cases as well as purses that double as boom boxes, with built-in speakers and the ability to plug and play iPods.

Indeed, the cultural juggernaut that is iPod has spawned a new class of entrepreneurs such as Joe Davis, a metal machinist who spent a slow afternoon designing a case for his iPod Shuffle. Friends soon began asking him to make one for their Shuffles.

"I heard over and over, 'That's really cool,'" said Davis.

He turned his cases into a business, A-1 Quality Products, which now makes metal cases, sold under the names "iKeychain" and "iArmor," for iPod Shuffles, nanos and minis. The metal cases are built for durability; in his booth at Macworld, Davis showed a video of a truck backing over one of his metal iPod cases, with the case surviving intact.

The iPod economy has created its fair share of entrepreneurs, but it's also been kind to big business. By far, one of the biggest beneficiaries of the iPod gravy train has been Belkin, which also happens to be one of the largest exhibitors at Macworld. To date, the company has created more than 100 products for the iPod.

Belkin's Downey wouldn't comment on how much of the privately-held company's revenues come from its iPod accessories, but he did say that while the company's roughly 100 iPod-related products account for a small portion of the thousands of products Belkin makes, the iPod gadgets account for a "significant" portion of Belkin's sales.

As newer iPod models get released, so do new products.

Belkin announced a slew of new products at the show, including a system that allows consumers to show content from a video iPod on screens already installed on seatbacks in cars and SUVs. A charger that plugs into the cigarette lighter connects to a docking station; cords running from the charger plug into the TV screens.

Belkin also launched products for the iPod and iPod nano that let users charge and listen to iPods in their cars and come with FM transmitters that let users view radio station frequencies on their iPod screens.

A corner of the Macworld show floor included several autos with iPod-related gear installed. Cars are one of the biggest drivers of the iPod accessory market, with Steve Jobs announcing during his keynote speech yesterday that in 2006, 40 percent of cars sold in the U.S. will offer iPod integration, or cars built with built-in iPod docks so that users can simply plug in their iPods and drive.

Apple announced on Tuesday a deal with Chrysler (Research) for iPod integration in its cars, but one of the first automakers to offer iPod integration was Mercedes-Benz. In January 2005, Mercedes and Apple unveiled a full iPod integration kit that lets users listen to iPods through the Mercedes audio system and lets them select songs via the car's steering wheel -- leading one analyst to call such a car "the ultimate iPod accessory."

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