Vodafone have announced the "Vodafone Access Gateway". As you can probably guess from the name, it's an in home "micro-cell" that transports up to four 3G voice calls over your home broadband connection. No word on 3G data or GSM only phones.
It would be great at my parents house, as Vodafone's signal disappears about 2m inside the house. Less useful for me in up in London, where I get a full strength signal at home.
It will be available July 1st has 3 different prices - £160 one off, £5 a month or free as part of a price plan. No word on if getting it "free" means getting a gateway in lieu of a phone (though I bet it will).
One thing - Vodafone are claiming it's the first of it's kind in Europe. I guess technically it is - but I do recall that BT offered mobile phones that would switch to VOIP in the home. The biggest difference is that the Access Gateway should work with any 3G phone (that's on the Vodafone network) and not a small range of specialized handsets.