At present, if customers wish to have access to Sky+ in more than one location they must get another box installed. Sky refers to this as its multi-room option, which is currently used by more than 1m subscribers.
The new device will mean that one box can serve two rooms and let viewers record and play back two different programmes on separate TV sets at the same time
The device, due for launch next year, has 'just gone into testing mode,' according to BSkyB managing director, customer group Brian Sullivan.
Speaking to Broadcast, Sullivan said: 'We are going to spend a lot of time perfecting the user interface and I hope it will be ready to launch in the first half of next year. The rational is that it is a better way of delivering the multi-room experience.'
No prices have been revealed.
This is the first co-production between Sky and Amstrad since the latter was acquired by the satellite company for £125m last week.
Meanwhile, Amstrad chief Sir Alan Sugar is planning to leave the company once the merger with Sky is complete.
The Apprenticestar told The Sunday Timeshe was in discussions with Sky over staying on as a consultant for its technology interests but otherwise planned to turn his attentions to growing his property business.