Well, I recently saw some wireless headphones at a store, and did a bit of research. I found all the usual companies (Pioneer, Sony, LogiTech, Sennheiser...) until I searched specifically on latency. I need low latency to be able to use them for DJ'ing, and most don't spec the delay between sound input and sound output. What turned up was a company called Amphony (which I hope is a mashup of "amplifier" and "phono-", and not "am" and "phony"!)... reviews of their headphones are good, and they also have a wireless digital audio link system. Their high-end products are using the 5.8 GHz band, which is currently fairly interference-free.
10 years ago, I was bullish on 5.8 GHz unlicensed ISM (instrumentation-scientific-medical) frequency band technology; in the past couple of years, it's started to hit the market big-time. Next up: the chunk at 24 GHz. This is a bit harder to exploit, but will allow some very cool applications when it does hit. Look for a few high-end products in that band in about 4 years, and mass-market stuff in about 8 to 10 as the 5.8 GHz band gets as crowded as the 2.4 GHz band is just starting to get now.
I should mention that I generally avoid sticking RF transmitters to my head for extended periods of time, although the research I've found suggests that any link between cellular phone use and cancer is tenuous at best; the headphones are, as best I can determine, receive-only, though.
Anyway, I think I've found something for both of our wish lists!