We are looking to implement a group -voice- chat in the browser using node.js on the server. Is this possible?
If you want your solution to be purely JavaScript based on both, server and client side, then you would probably have to wait for the WebRTC, Device API or media capture API and then implement node.js backend for it.
Other than that it is, I would say, a question of Flash oriented APIs on the client side (for accessing devices such as cameras or microphones) and some kind of interoperability with node.js backend in case you don't want to take advantage of Flash Media Server or Red5.