Just yesterday I released version 2.2.5 of Kontalk on Play Store, but XMPP development continues.
I installed a first development and testing Kontalk server on this host. It can be used with a preview version of the XMPP client available here:
Registration is achieved in the usual way — through SMS. For now you will only see users registered on the XMPP network — on the final release you will see older versions users too.