Blab is a live-broadcasting app that streams video to a “Public” or “Unlisted” stream (host’s choice). With 4 “Open-Seats” available in each Blab, topic-driven conversations are shared with a live audience. Interaction also occurs via text through live audience participation. While anyone can call-in (or ask) for an “Open-Seat”, only the host can approve who receives the spot.
I had never heard of Blab before, but it looks to be a pretty neat alternative to Google Hangouts.