[LAU] Measuring BPM

[Chip VanDan]

Okay, so I know the old trick of using a stopwatch and counting,
that's easy enough, but I always seem to screw it up.  I have a
tendency to set my BPM by the speed of my echoes, and I'm terrible at
counting or doing anything at all while I'm playing.  Is there any
software out there that will measure the BPM automatically through
MIDI inputs?  Preferably one that will run with Jack?  My preferred
setup is Zyn and Hydrogen running at the same time, both being
recorded simultaneously with Ardour.