Well, I have a few concerns about this such as how many people on BYOND actually have a microphone & how many people would actually use it on a BYOND game even if they had one...?

And here are a few ideas that could make it more helpful and a few more concerns.

1.Make it so you can do some voice recognition on the voice so you can make the game interact to commands given by voice.

2.Possibly make voice chat capability inside the pager so you can start/accept voice chat's through there.

3.Make a way to disable the microphone if you want to use it for something else in windows such as MSN/Voice Recognition in vista/windows 7 & such & don't want people in the games to hear you.

--Anyways i'd probably implement this in my game once it gets created making it so you can hear all your team-mates in a freeze-tag game for example, or hear your opponent's once their close to you in the game or private chat, or possibly always hear people close to you.

If it had voice recognition could tell AI to move up or fall back or someting, which would be nice, but as for how many people would use it, how many games, etc... it might not get implemented, but I see the possible potential for such a feature, but it would probably take quite a while for them to add it, especially all of the possible features I have sugggested for voice chat capabilities

There's a lot more that goes into it than that. I can't see this actually getting priority, mostly because there are other alternatives (skype, ventrilo, teamspeak, what have you). Most games that implement their own voice chat mechanisms are already MMO-styled games anyway, not the engine itself.
Bandock did something like this with a DLL, which could be used to recognize server side, but it couldn't go from client to client. Lots of issues surround that.

While I agree that if you want it done now you should probably go with an alternative seeing as how big something like this would be to begin with, but not having this added in the feature at least I think would be a mistake, while there are probably pretty good alternatives you make every user use whatever you use to chat with & you leave it up to the developer to make sure their implementation warns you about the use of mic, that the game actually even uses it all, mute buttons & volume buttons & such which while would be standard may not be in quite a few implementations, especially when their just trying to get something working at all in general.

With BYOND you would have a way to disable and enable the use of the mic, BYOND would warn you that it actually uses it on that game, or indicate somewhere, and there would be no question as to whether or not it will work correctly, you don't have to try many different implementations & codes to get something to work, with the kind of sample given, it would be really easy to implement into any game.

Anyways, as for basic mute/volume controls BYOND's implementation wouldn't have them standard, mute would obviously be like turning on/off sound for a BYOND game is & volume possibly by windows or by the game outputting a certain volume level which would be defined somewhere in the code possibly at which volume and sound attenuation for people hearing you in view() would be & such.

Also, for just general attenuation capabilities & direct voice chat(not recording from mic then playing back a given message.) If I wanted record then playback i'd use windows voice recorder then make it play a file off the computer to everyone on view for example, if that was the case.