I was a little worried in ordering this item, as trying to find out anything about it is very difficult. At the time of my purchase it did not even appear on the Sony website.
However, I needed not worry. You bascially need to have a Sony system that is S-Air compliant, I have the Sony BDV-E370. You then plug a module into the back of the main E370 and a module into the WAHT-SA2, you then wire the speakers to the WAHT-SA2 and hey presto, wireless surround speakers, everything you need is included.
I set this up inside five minutes and the sound quality that comes from the wireless speakers is equally as good as the wired front speakers.
All in all a great purchase.