Google Wave 2.0?
It's got a lot more focus than Wave had at launch. Wave's big problem was that it introduced so many new features at once, in one product. No one could figure out what to do with it, and it was very confusing. This looks much more focused, although its unclear what it offers over Hangouts or FB messenger. The only feature it seems to add over facebook's product is a focus on conversation subjects versus social groups…
Which does make me wonder what problem Hum is solving. What group is saying, "X is really painful for us"?