T-Mobile announced a nationwide VoIP-based landline phone service that offers subscribers unlimited domestic calls for $10 a month. The service, called T-Mobile @Home, is the lowest priced unlimited plan in America. The T-Mobile @Home is available exclusively for T-Mobile customers, effective July 2, 2008.

T-Mobile customers can add T-Mobile @Home service to a qualifying T-Mobile wireless plan (most plans priced at $40 and up qualify) and get unlimited nationwide long-distance calling, plus call waiting, caller ID, three-way conferencing, voicemail, call forwarding and other features like custom ringback tones. The @Home service also allows customers to port their existing home phone number.

Like other consumer VoIP services, the service includes an in-home gateway that connects to the Internet and can be used with a standard corded or cordless phone. However, unlike other VoIP providers, customers must buy the T-Mobile @Home HiPort™ Wireless Router for $49.99 and sign a two-year service agreement; early termination fees also apply. The router also supports the T-Mobile Unlimited HotSpot Calling service (formerly known as HotSpot @Home Talk Forever Mobile) also priced at an additional $10 a month. (For information on the HotSpot service, please see our newsletter on the topic here.)

When we wrote about the @Home service market trials in Dallas and Seattle earlier this year we questioned the affect of the offer on competing landline plans: According to an internal T-Mobile study in these test markets, virtually all customers (97%) who had a traditional landline phone service reported dropping that service since adopting T-Mobile @Home. Looks to us like T-Mobile may have a winning value proposition for its wireless customers who aren’t quite ready to “cut the cord” on their home phone.