Groove Basin (http://groovebasin.com/ http://groovebasin.com/) has a feature like that. I haven't tested multiroom in the same place, but have used it to stream

Groove Basin (http://groovebasin.com/ http://groovebasin.com/) has a feature like that. I haven't tested multiroom in the same place, but have used it to stream at home from the office server for example.