HotSpot@Home cellular and Wi-Fi service

The new service, HotSpot@Home, allows a subscriber to place calls from a mobile phone using cellular and Wi-Fi networks, whether a home wireless network or a hot spot operated by T-Mobile.

In my own testing, I found the service a reasonable first draft of what could become a reliable alternative to both all-cellular networks and an emerging set of Wi-Fi-only phones. The marriage might even save money — for both T-Mobile and its subscribers. Carrying calls over Wi-Fi networks costs the company as little as 20 percent of the expense of calls handled on a cellular network.

All calls originating on a Wi-Fi network to numbers in the United States are included in a monthly fee of $20 for a primary phone and $5 for additional phones in a family plan. The Wi-Fi plan must be coupled with a traditional voice cellular service plan of at least $40 a month.

Marrying the Cellphone to Cheap Internet Calling - New York Times