T-Mobile supposed to roll-out its Hotspot at Home service Nation-wide this summer.

T-Mobile offers the Wi-fi phone service currently in selected areas. The offer Nokia mobile phones that can seamlessly transfer calls from the carrier network to available wireless network when they become available.
T-Mobile would also be able to allow customers to connect home phones to this "one phone" offering, which would allow them to compete with landline operators.
Via the WSJ (Subscription).
See also this T-Mobile site that promotes T-Mobile HotSpot @ Home.