A new MP3 player expansion slot for

Handspring Visors is poised to hit the market in October, heating

up the competition in the booming market of handheld computer

devices and their accessories.

Good Technology, Inc. planned today to unveil its SoundsGood audioplayer at the DEMO Conference in Pasadena, Calif. The device turns a Handspring Visor into a digital music player. With 64 megabytes of built-in memory, the company claims it gives the user more than an hour of music.

Innogear Inc., based in Morgan Hill, started shipping a similar product for Handspring users a week ago.

Good Technology, a Redwood City-based developer of add-ons for personal digital assistants, is hoping to tap into the scorching market for handhelds. Market researcher Dataquest expects global sales of computer handhelds to quadruple in the next three years to 32 million units worth $7.2 billion.

At the same time, Good Technology is responding to the growing popularity of MP3 digital music technology. The company said nearly half of the users of Visor have expressed interest in an MP3 module for the device’s Springboard expansion slot.

Costly Add-on for Inexpensive Visor

Handspring’s Visor is a cousin of Palm handheld devices that use the same operating system, and the Visor has quickly become a popular alternative, grabbing 27 percent of the retail market, according to several research firms. The Visor, which sells for between $149 and $249, was the first — and, for at least a while longer, is the only such handheld — to feature an expansion slot capable of transforming it into everything from an electronic book to a global positioning device.

Digital music players on handheld devices are nascent but not completely novel: The newest generation of PocketPCs made by Compaq Computer Corp., Hewlett-Packard Co. and Casio Computer Co. have the capability. But unlike the smaller, sleeker Palm devices and the Visor, sales of PocketPCs — which sell between $499 and $599—are still struggling. In addition, the MP3 accessory made for the Visor consumes less power, analysts said.

“If you have a Visor and you like the idea of an MP3 player, you’re really going to want this thing,” Martin Reynolds, vice president and research fellow at Gartner Group’s Dataquest, said of the SoundsGood player. “This is an emerging technology to watch.”

But whether consumers are ready to pay for the digital music accessory has yet to be seen, said Ken Smiley, a senior industry analyst with Giga Information Group.

The SoundsGood audioplayer is priced at $269 — more than the Visor itself.

“It’s a nice device,” Smiley said, “But I’m concerned the price is not going to set well with the consumers who purchased the Handspring for the reasons they purchased it for.”