Called 'Femtocell' it's been released by Vodafone, the first operator in Europe to get it out to customers.
But at £160 it's not cheap - and you need a decent broadband connection to make it work.
Lucy Marks, 23, from Stroud in Gloucestershire, has been testing it.

"My house is a bit upside down. You come through the front door and go downstairs to the lounge and kitchen, then upstairs for the bedroom.
"It makes it a nightmare for getting any kind of reception on my mobile."
But since she started testing out this new technology about one month ago she's only ever had full signal on her phone.