Let the hive mind of Engadget get that for you.
"I am looking for a device that will stream sound from one source to several recipients. For example, I want to stream sound from my TV or stereo to my phone or MP3 player that has radio and Bluetooth capabilities. I have looked into radio transmitters and they seem like a decent choice, but I can't find one that uses external power (USB or from the plug) and I would want one with a transmit range of around 50 meters. Thanks!"
Excellent idea, but given the cost of category 5 cable, unless your in dire straits, this really isn't an option.
Yeah other than you already have coax cable probably going to most rooms in your house (and coax is cheap too). I wired my house with cat 5 and it's a pain in the butt. This is a good idea. I might use it to expand the network to other areas.
In my 1917 built home there is no wired Cat5 any place but i do have coax in several rooms so this is a MUCH better option for me.