> Coming soon to the USA?
>
> T-Mobile bundles Wi-Fi with Web 'n Walk
> <http://www.theregister.co.uk/2008/01/09/t_mobile_bundling_wi_fi/>
>
> T-Mobile customers signing up to Web 'n Walk Plus (or Max) will get
> free access to the operator's 39,000 hot spots from January. So for
> £12.50 a month users can get 3G and Wi-Fi connectivity, and be
> allowed to use instant messaging too...
>
> Web 'n Walk is already one of the more attractive options for users
> wanting mobile internet access, though usage restrictions on the
> basic service limit it to general web browsing. The Plus, and Max,
> services offer a higher fair-use level and permission to use instant
> messaging and such like. Charging users again for T-Mobile-branded
> Wi-Fi access always seemed harsh, even if it comes with truly
> unlimited quantities of data.

It's possible to call from a wifi-enabled cellphone to another phone
without even using a carrier or even a SIM card. Check out the youtube
demo at http://www.youtube.com/watch?v=aPPrKUKkc8Q which shows how you
can use Fring software http://www.fring.com on your wifi phone to make
calls using any wifi connection. The calls are free between Fring users.
Calling costs vary if you're calling a cell or landline phone, depending
on your VOIP's outbound calling plan. Fring supports VOIP through SIP,
Yahoo, MSN, Skype, GoogleTalk, among others.

I'm not sure if using Fring through T-mobile's wifi connection will
offer the same savings if one uses it with a cheap VOIP plan, or if the
calls will count against your minutes.