With people already spending billions on ring tones, wallpaper and games for their phones, analysts and retailing executives say they believe it will not be much of a leap to get them to use their phones to buy shoes, books and laptops.

"This will start to show up on the radar screen in 2006," said Roger Entner, an analyst with Ovum, a technology consulting firm in London. "The more different pieces we add to these Swiss Army phones, the easier it is to get user acceptance for the next application. And especially around next Christmas, the convenience of shopping on a computer or a cellphone will beat the mall hands down."

One of the challengers to eBay, Overstock.com, which sells travel services and products for fixed prices and at auction, also recently ventured deeper into the wireless realm. In November it started mobile O, where cellphone users could use their phones to browse and buy anything on Overstock's Web site.

The service was initially intended for customers of Verizon Wireless, who pay $5 to activate it. Jeanne De Sanctis, chief executive of mRocket, which developed the Mobile O application for Overstock and markets similar services to other companies, said Mobile O would be available on Sprint this week.

Patrick Byrne, Overstock's chief executive, has personally helped develop the company's mobile efforts, investing more than $200,000 of his own money in mRocket and lending Overstock engineers to the project. "My hunch is that this is going to start really happening more in '07," Byrne said.