Pulver ships WiSIP: Voice over IP over any Wi-Fi network: This portable phone puts Wi-Fi and VOIP into a single package for $250. It was announced last October at Pulver's VON conference, but Joi Ito just received his, and the Pulver site still says that it's shipping at the end of January 2004.
The phone works by default with Pulver's Free World Dialup network, but can be reconfigured to work with any SIP (Session Initiation Protocol) gateway. If you use a VOIP service with access to the public switched telephone network (PSTN) and which provides its SIP details, you can configure the phone to make real calls. The phone handles WEP, not WPA, and MD5 authentication, which is considered weak for untrusted, sniffable network uses.