Coming Soon: Cellular + WiFi Phones
Later this year, T-Mobile is expected to roll out plans for a new generation of cell phones, ones that work on both cellular networks and the Internet (via wireless / WiFi connectivity). The idea is that when a person is in a WiFi area, they will use the Internet for their voice calls; saving their plans's anytime cellular minutes for when they are in an area where a connection isn't available. The incremental charge for this service, beyond the cellular plan cost, will likely be pretty nominal.
These phones might prove to be the thing that leads to more people ditching their home phone, and going totally wireless. One of the problems with doing so today (going totally wireless) is that in-building or in-home cell signals are often weak. This would address that issue, as those with WiFi in their house (high speed Internet with a wireless router set-up) will be able to use that signal inside the home.