The transport of the JACK Audio Connection Kit allow many dissimilar applications to synchronize their timing (bars, beats, ticks, etc.). There's often synchronize this with devices (usually synthesizers) with the older MIDI Clock. This is a command-line application that simply sends MIDI Clock pulses that reflects the state of the JACK Transport.
For more information, see the README file.
Source code repository (Git):
git clone git://gabe.is-a-geek.org/git/jack_midi_clock.git
Robin Gareus has been doing a lot of excellent work on this program, so you might also be interested in checking out his sources: https://github.com/x42/jack_midi_clock
Send bug reports to gabriel@teuton.org.