Prosody can double as your UnifiedPush server an any Conversations app can be configured to be a low-bandwidth UnifiedPush client. This would XMPP can fill as role of chat as well as unGoogled notifications. If you use something like JMP you could have a secondary or primary phone number. With some gateways you could puppet some proprietary chats. Seems you can get a lot of value out of that chat app.