John is correct that a good wireless IEM system like the Sennheiser G3 would be suitable for what you want--but there's an old saying that you can spend hundreds or even thousands on a wireless system that's almost as good as a $20 cable. It's probably worth considering why you really need it to be wireless--there's various things you can do on wired systems (for example a "coily" cable to add range and avoid tangles) that might give you a cheaper solution.
That's what I do. I drink and I know things.
-Tyrion Lannister (and Bobbsy)