Passfilter provides you with a terminal that has certain words blacklisted. Upon entering a predefined character sequence (defined as an MD5 sum), the terminal will erase the written characters with backspace, give an error message, and wait until the line is finished with the Enter key. The use case would be to stop you from accidentally entering passwords to IRC or possibly to other hosts, which could be compromised and could be logging your entry.
STALLioN is a cross-platform C/C++ library for creating coherent CLI/Terminal programs on multiple platforms with one codebase. It aims to provide a consistent development API across multiple platforms so that separate code does not have to be created for each (often very different) terminal interface.
Jaro Mail is an integrated suite of interoperable tools for GNU/Linux and Apple/OS X to manage email communication in a private way, without relying on online services (in fact, encouraging users to store email locally). It mainly features a system for mailinglist filtering, address-book integrated whitelisting, and long-term email storage and archiving with functions for fast search and usage statistics. It makes internal use of customized versions of popular Unix tools like Mutt, Fetchmail, Procmail, Mairix, and Msmtp.
utfout is a command-line tool that can produce UTF-8 (Unicode) strings in various ways and direct them to standard output, standard error, or direct to the terminal without the need for shell support. Strings can be repeated, delayed, randomly-generated, written to arbitrary file descriptors, interspersed with other characters, and generated using ranges. printf(1)-style escape sequences are supported along with extended escape sequences. utfout(1) sits somewhere between echo(1) and printf(1).