tbclock is a dirty little app that displays a full screen binary clock in your terminal (using curses). It is quite simple and features modules like "guessbin" a little time guessing game and "chrono" an accurate timer with tenth of seconds.
In any situation, you will need ncurses and its headers (libncurses5-dev for Debian). Then, the procedure is quite simple:
$ ./configure $ make $ sudo make install
FreeBSD users can simply type "pkg_add tbclock" thanks to the work of Andrew Pantyukhin (sat at FreeBSD). Thanks Andrew!