OMG. so much this++
I wonder how they're avoiding using GCM like textsecure was
I think it is because they only handle SMS's. It doesn't have the push messaging part. You still need TextSecure for that.
I don't know - anyone got time to review the source? - but if they're only doing SMS, they might not need it; after all, SMS is already 'push', and it was only needed for push notifications for the data channel.
We've removed the need for GCM since SMSSecure only deals with the SMS/MMS functionality.