Companies that have capitalized on accessories for Apple Inc.’s iPod are hoping history will repeat itself as they ready iPhone accessories for the smartphone’s debut Friday.

Everything from earphones and adapters to special chargers and cases for the iPhone will begin hitting the market Friday, with many slated for release in July and August.

Products engineered to be compatible with the iPhone will carry the “Works with iPhone” logo on the packaging.

Niles, Ill.-based Shure Inc., an audio products manufacturer, says its music phone adapter (MPA) will allow iPhone and Motorola RAZR V3i users who have its sound isolating earphones to “switch seamlessly” between using the accessory for music-listening and talking on the phone.

Apple CEO Steve Jobs has predicted that 10 million iPhones, or about 1 percent of the global cell phone market, will be sold in 2008 despite a high initial price tag of $499 to $599. 

Apple has sold 100 million iPods since its release almost six years ago, and more than 4,000 accessories have been made specifically for the iPod.

Chris Lyons, Shure’s manager for product marketing and retail support, says the company has eagerly awaited Apple’s release of the iPhone and expects Shure’s MPA to do very well.

“From the last several years of selling earphones just to iPod users, we developed this rule of thumb that about one-third of iPod buyers buy a new pair of earphones within about 90 days of buying the iPod,” Lyons said. “What we don’t know is whether that same rule of thumb will apply to the iPhone… We think [it] will mostly because with the iPhone there’s more emphasis on the music aspect.”

Shure’s first model of the MPA is set to be released in August with a suggested retail price of $39.99. The product will be available on Shure’s Web site and select retailers.

XtremeMac Accessories Inc. will release an international iPhone charging set to several retail outlets in July to match its international iPod charger. Its basic wall charger, InCharge, will be $30 and its car charger, InCharge Auto, $20.

InCharge Travel is a set that includes wall, car and airplane chargers in addition to four wall adapters for international travel use. The set will cost $40. All chargers will be available on the company’s Web site July 28.

“This is really the first and best convergence of a phone, iPod and computer. There are a lot of opportunities there,” said XtremeMac’s U.S. Retail Merchandising Manager Chris Doran. “Given the increasing demand for cell phones and given what the iPhone offers [cell phone users, 10 million] may not be such an optimistic number.”

Griffin Technology Inc., a company known for its Apple accessories, has new products ready for the iPhone’s launch Friday. These include Griffin’s PowerJolt for iPhone, a snap-in case and a leather holster, each of which will cost about $25 to $30. These products will be available only at Cingular and Apple stores and online at Griffin’s Web site.

“With the price of the iPhone… we really see the purchaser buying those accessories [a case and car charger] right away,” said Alex Birch, Griffin’s category manager. “We expect our success with products to be very high.”

More Griffin products, including an arm band and other cases, will be released at a later date.

Marware Inc. and Belkin International Inc. plan various iPhone cases, some evolving from previous versions of iPod cases. Prices for some of the cases will range from $15 to $30 and are slated for release later this summer.

While hopes are riding high among accessory manufacturers, some analysts are more cautious about the iPhone's initial success.  

Andy Hargreaves of Pacific Crest Securities in Portland expects about 2 million iPhones to be sold this year. His estimate for 2008 is for 6 million to be sold, far short of Apple's forecast for sales of 10 million.

As prices for iPhones come down over the next five years, Rod Bare of Morningstar Inc. writes that the handset could gain a 3-percent share of the global handset market, said Rod Bare of Morningstar Inc. in a report following Apple's fiscal second-quarter results in late April. 

If that holds true, then accessories for the iPhone could ring up strong sales and profits for their manufacturers long after Friday's much-anticipated debut.