A company called Meru Networks introduced an AP and controller aimed at supporting voice over WLAN: The system includes a QOS mechanism that gives priority to voice.
Meru also uses a similar method as AirFlow to essentially eliminate the time it takes to hand off a call from one AP to the next, which currently takes too long to support a voice call. Meru and AirFlow do that by associating clients to a single MAC that lives back in the network at the controller. That way clients don't have to re-associate with each new AP because there's only one MAC to associate with.
I suspect Meru is greatly exaggerating how many users can use a single AP at once. It says that one of its APs can support as many as 100 users. Most vendors say that today their APs can support 10 simultaneous voice calls but will usually concede that half that number is realistic. Meru would have to be doing something pretty radical to improve the number of simultaneous users that dramatically.