@dimitrisk you should port https://silence.im to Linux Mobile. Could even run it in SXMO in sxmo_hook_tailtextlog.sh so the messages would be encrypted-at-rest.
@dimitrisk Personally, I'm more committed to XMPP, but if someone wanted to manage this project, it should be pretty easy: a library exists (https://github.com/signalapp/libsignal-protocol-c). I'd be happy to give guidance and help test or code.