Skype for iPhone launches tomorrow with Wi-Fi calling functionality

Skype, the popular voice, video, and instant messaging chat software parented by eBay is reportedly coming to the iPhone App Store tomorrow as a free download.

When a user's iPhone is connected to a Wi-Fi network, they will be able to use their Skype account to make free Skype-to-Skype voice calls, send instant messages, and make outbound calls to other mobile devices or landlines for a fee.

Just a week ago, Skype 3.0 launched in beta for Windows Mobile. A version for BlackBerry will be released as well in May, and versions for Symbian and Android are expected to follow.

These versions will differ from the commonly-found Skype Lite client, which allows Skype voice calls -- and little else -- to be placed over regular cellular networks. This version has already found its way onto most mobile operating systems.

The Skype for iPhone interface offers five tabs along the bottom of the screen for open chats, chat history, a dialer, "my info," and contact information. The software automatically integrates the phone's address book into its contact list for SkypeOut calls.

Skype will be competing against Truphone, which has been available for the iPhone since last year and offers similar functionality.