While I love to be wireless as well, I don't think these products will give you results that you are happy with.
Wireless printers are out there if you look for them. HP makes two good ones, the 2510 (scan, print, fax, memory card slots) for about 400, and the HP 5850 i think is your basic deskjet with Wireless, or networking.
As for sound, I just hook up my iPod to the stereo. If you need more control, they have that remote thing from Keyspan, I believe. Its on the apple website.
That is really all the wireless I need. I take my laptop all around the house, and can printer from every, but I also have my desk for when I need to use power/ plug in stuff to the PB.
While all wireless would be cool, I don't think it is the way to go...yet.
ps, check those wireless audio transmitters, such as the creative ones, I think linksys makes one too, that they are Mac compatible. I can't speak about the creative one, but I think the Linksys one is not.