The hack itself is simple. [daffy] locates unused USB data lines, adds in a 5V voltage regulator to supply USB bus power, and then connects it all to a USB sound card. Hardware side, done!

[Rosenberger31] did a nice job of adding a USB port to his 2010 Toyota Prius ... There is no data connection here, the port only provides 5v regulated power to devices plugged into it.