Inspired by the rhythm mechanic in a game prototype created by students at UCSC, I decided to make my own beat matching toy. Try it here: http://adamsmith.as/typ0/k/fralbs_pulse/ -- give it a minute to load the music. Once it is running you can click in the box or press keys while the applet is active to try to match the beat. The audible feedback comes in after 32 beats.
I haven't tested it on more than one computer, so the (critical) timing may be horribly off.