Mumble is a popular, open-source voice conference program aimed toward gamers. It is superior to Skype, TS3, Vent, and Dolby Axon in terms of simplicity, resources, and sound quality.
Mumble has support for positional audio. Here's an example of positional audio being used
League of Legends should support Mumble's positional audio. I would prioritize this over implementing a replay system because of the combination of these reasons:
- This is fast and easy. The code is already written for you. It would take a week of work. (absolute maximum; it really only needs a day).
- This would benefit everyone who uses Mumble to communicate for LoL
- The Mumble Link interface is cross-platform. No need to worry about another thing to port for the beta OS X client.
- Riot would gain reputation among serious gamers and in the open source world. Free PR, anyone?