Cups Messenger truly leverages the capabilities of a personal server. It is a direct messaging application which allows you to send encrypted messages over the Tor network to another user with the Cups Messenger app. These messages exist only on the two personal servers involved in the communication, not in Facebook's cloud, not on Google's servers.
To learn about how to use Cups, read our blog post.
The Cups Messenger app is an open source project developed by Start9 Labs: https://github.com/Start9Labs/cups.
There is a mobile application presently in the works which will provide a slick user interface for sending encrypted messages via your Embassy's Cups application. For the time being, there is a more bare-bones command line tool which accomplishes the same task: https://github.com/Start9Labs/cups-cli