Blitz – Secure Chat

Blitz is a new free messaging service. Its significant advantages are security and privacy — all messages are end-to-end encrypted, the server does not store any activity, messages, cell IDs or any other personal data.  Users' authentication is anonymous - it has no connection to your phone contact list (names, phone numbers or email addresses). 

There is also a number of additional security measures like pin-code app lock, messages auto-expiration, deletion of a message on both phones and more. Commercial corporate version of the app's is also available - server software can be deployed on premise.