At CES there were at least 2 companies selling extremely flat speaker wires, paper thin. Using spray glue you can glue these wires to the wall, preferable around the baseboard where it's less noticibale and depending on your tollerance for perfection, either paint over them or spackle over them and then paint. If you have textured walls, buy a can of texture to splatter over them and paint, you'll hardly notice them. You'll have to scour the web for them, didn't keep much info from the show.

They did have wireless speakers at CES but they tend to be very low end and the ones that did run on batteries were short lived, you'll be lucky to see one movie. The ones that use the A/C powerline were better but depended on you having A/C on the same circuit where you want the speakers. Even then, not much was available, mostly conceptual.

Suprisingly, if you shop around you can find an electrician to do it for not too much dough. CC told me they charge $200 to install a pair of in-wall speakers and run the wires.