Not 100% certain if you mean just wireless speakers, or wireless connectivity from one system to others? If the latter:
I used a wireless system that an acquaintance had let me try out for my woodshop. I was building some cabinets for his electronics class when I brought up the subject of playing music from the same source throughout the house. He brought me a wireless transmitter which I connected to the main system in my living room, then I simply tuned to the selected frequency to pick up the signal on other tuners.
It worked pretty well except for when using in my shop with machinery running, the machinery caused issues with static interference which was quite annoying. Unfortunately this was quite a while ago and I do not even remember the brand, much less the model of the unit.
If you get a decent system and aren't using it in a hostile environment such as a woodshop, you will most likely find a wireless transmitter to your satisfaction
