Overview
Here is a Game Boy LSDJ / Nanoloop 1.x sync device that shows up natively as a USB MIDI device, thereby requiring no drivers and no power beyond the standard USB connection.
In terms of soldering, it is very easy as well, as it only requires two connections for each Game Boy sync cable, and that's it. Also, the source code can be easily edited to fit your own needs.
This is a very cheap and easy project to make: the Teensy board costs $16. You will most likely already have a USB A to mini B cable and a Game Boy link cable.