Unfortunately I have yet to find a good set. Most have poor sound, do not match tonally with your existing speakers and are very underpowered. They can also have problems with signal interference.
The dream of wireless high-performance speakers is still unfulfilled, but a few manufacturers offer "wireless" speakers that receive signals via radio waves or infrared light--great but they still need to be plugged into the wall for AC power. Battery-powered wireless speakers just won't cut it in any sort of quality-oriented surround system.
I set up the kef 2005.2 system last week. I have wood floors, doorways between the front and back walls and did not want to have to pull wire through the walls and attic.
I bought the Rocketfish wireless rear speaker module from Best Buy. $99 bucks and if it did not work I have 30 days to return.
After a week I have to say I am pretty happy with it. No front to rear wires but the rears have to be hooked up to the receiver which is under my couch and out of sight.
Works on 2.4 ghz. I was leery of this because I have a wireless computer network and a phone system using the same. No interference problems with the different networks.
This is worth a try for anyone looking for a wireless rear solution.