Hi, I am the author of Tortoise (as well as the gen_mqtt client/wrapper)
Tortoise is the successor to gen_mqtt; it doesn’t quite work the way I described in a previous post (I have a full time job and all that, so time is scarce which conflicts with really ambitious projects) but I think Tortoise is really nice at separating the MQTT semantics from the Elixir semantics; right now it support publishing and subscribing to topics with Quality of Service 0 through 2; TCP and SSL transports, and it behaves pretty well when it reconnect to the broker.
I still have some way to go before I can call it 1.0, but I’d say it is usable now; everyone who uses gen_mqtt should switch to Tortoise. Don’t be shy if you have any questions 
