WiFi phones for use with Skype or SIP based VoIP providers (such as Gizmo) are slowly becoming available. For instance, the following phones are already available on Amazon:

The Skype phones are also available in the Skype Store

However, note that most of these phones don’t include a webbrowser, so there is no way to authenticate yourself at public WiFi hotspots that require browser-based authentication. This is quite a big problem, IMO.

I would hope that the second generation of these phones overcomes this limitation. Another possibility is that hotspot vendors could provide better support for non-computer based devices. However, since many hotspots are provided by telco owned companies I would imagine they will delay this for as long as possible.