VOIP during a game is something you definitely want to do in a seperate thread, and multithreading plugins are possible, they tend to be extremely unsafe.
It would probably be a lot better to make a seperate program to do voip and then use a plugin to communicate between the game and the voip program to organize the chat by whatever the needs of the game are.
However, this is something that is definitely a major bit of work and isn't likely to be free due to the sheer amount of work that would have to be done.
As far as I know, nothing of the sort even exists yet.
When the power of love overcomes the love of power, the world will know peace.