Mobile operator O2 is to offer phones that switch from mobile to land networks, offering customers a 'one number' service.
The launch is scheduled to coincide with the switching on of O2's 3G network in late 2004 or early 2005.
It features Bluetooth technology and taps into the bandwidth offered by a user's broadband pipe, either DSL or cable.
As long as it is in range, currently around 100ft, the new handsets will automatically use the cheaper broadband line at tariffs comparable to, or cheaper than, current BT rates.
All the user requires is a "higher level application that sits on the DSL/cable backhaul", according to O2 chief executive Peter Erskine.
The telco plans to charge around £50 for the box, and trials of the service will begin in Marlow later this year before a full roll out in the Isle of Man in 2004.
O2 has already launched a version of the service in Germany, called Genion, which has impressed analysts.
Technology currently in development should extend the handset's range to one mile, and may be ready before the planned UK launch.
Meanwhile, the operator is to enter the wireless local area network (Lan) market, offering 1,000 sites centred on hotels, airports, conference centres and railway stations.
It has partnered with wireless Lan authentication and payment firm Excilan, and will charge via pre-paid cards and bundled packages added to the user's existing bill.