Actually, the "invisible wires" HAVE been released! See link below (their web site is under construction, so this is the best I can do for now). I haven't tried it and don't know the quality. I have tried the same company's RF remote control extender, and it works great. That might also help in your situation, so you could potentially control the central receiver from your remote listening locations.

http://www.terk.com/pdfs/LEAPFROG-LB.pdf