I had (actually still have) an X-10 Video Sender I bought a couple of years ago to beam mp3s (and the TV out from my video card) to the stereo and TV in the front room.
It worked "okay". The audio fidelity wasn't quite as good as I was expecting, although my expectations were kind of high. I can't really judge the video quality because as you may know, TV-out looks terrible even with a direct S-Video cable...
The problems I had with it (and the reason it's been sitting in a box for a year) is that it both interferes and receives interference from other devices operating at 2.4GHz... the worst was the microwave. When you'd turn the microwave on, loud static would come through my stereo speakers. It also causes static in and decreased the range of my Panasonic Gigarange cordless phone (static could be heard both on the phone and on the stereo when both were in use--double whammy).
So I got sick of it and it's in a junk box in my closet. I still have the microwave, and now have a CyberGenie (Ericsson 2.4GHz) phone, not to mention an 802.11b wireless network, so needless to say it's going to be sitting in that box indefinitely.
Hope that helps... I'd be interested in hearing about any alternatives that provide high quality audio (video too) and don't operate in the 2.4GHz range.
l2c