While only about a third of all Pocket PCs have Wi-Fi connections, Skype's popularity could spur more sales of the pricy handhelds, said Chris Shipley, executive producer of DEMOmobile 2004, a wireless trade show in Los Angeles where the new Skype software was unveiled.
"Skype is creating significant demand for mobile and other new-generation WiFi-enabled devices," Shipley said in a statement.
A test version of the PDA software debuted in April. Until that point, Skype's free software had been available only for personal computers.
Skype uses voice over Internet Protocol (VoIP), a technology for making phone calls over the Internet rather than the heavily regulated and taxed traditional phone network. Calls placed through Skype are free, but users must place their calls via computers rather than phones. Additionally, they can only call people who have installed the software, unless they pay extra through the company's, which lets customers place VoIP calls to landline and mobile phones for a per-minute charge.
By contrast, other companies, such as AT&T, with its CallVantage service, and, let customers place calls to any phone in North America. Subscribers usually get unlimited calling for a flat monthly fee.
Of providers of free VoIP software, Skype is among the largest, with an estimated 500,000 users. The largest commercial VoIP service is Vonage, which has about 200,000 subscribers.