There ARE wireless systems, but they tend to be expensive, not always 100% reliable, and many require a clear line of sight. You also need power for any speakers that are getting the signal wirelessly, so that means either speakers that have amps built-in, or a separate stereo amp at the back of the room that you can plug regular passive speakers into. So I'm not personally in favor of trying to use the wireless systems for speakers or subwoofers. That said, a couple of options are
Aperion Audio's wireless systems and
HSU's ULS-15 subwoofer that includes a wireless option.
To me, the best and easiest solution is to still just run wires and cables. Since you will be running wires to at least the front wall, really, it's just a matter of getting the wire runs from that front wall to the side and rear walls as needed.
One easy way to hide those wire runs is by putting them behind your baseboard or crown moulding. Or you can run wires under the carpet, or use the small gap between the outer perimeter of your flooring and the wall that is covered by your baseboard and/or quarter round.
Then it's just a matter of extending from the moulding to the exact spot where you want the speakers on the wall. For that, you can use paintable, flat wire, such as
Axiom Audio's flat speaker wire or the wide selection of
FlatWire Audio products .
So that's the route I'd go, myself. I think the wireless systems are more cost and hassle than they're worth. The idea is great, but in reality, they just don't stack up. Running wire might take a little more physical effort, but I think the results and the cost savings are well worth it. You'll need a little drywall compound, some primer and some paint to totally hide the flat wire and cable options, but you won't have to tear open any walls, and it's a pretty simple install. Running the flat wire the whole way will increase the cost, so try running normal wire or cable as far as you can, using your baseboard, crown moulding, carpet or perimeter gap to hide that wire and run it as far as you can. Then transition over to the flat wire for any runs that need to be out in the open.
Hope that helps!