Little-Scale demos NanoGroover – a device that generates Nanoloop sync data for two Gameboys, letting you sync them in some interesting ways:

• Two in the time of four (double speed)
• Three in the time of four (three against four cross rhythms)
• Four in the time of four (1:1; the sync is equal)
• Five in the time of four (quintuplets)
• Six in the time of four (triplets)

There are also controls for controlling the speed of sync (via a potentiometer; aka a “knob”) and interrupting / stopping the sync signals for either Game Boy, so that it stops.

Sort of an awesomely insane project – details on the hack are available at the Little Scale site.