Hmm...a bit hackish, but two zeros back to back, connected over SPI, would be able to transmit the keystrokes with minimal latency there. Course at that point,

Hmm...a bit hackish, but two zeros back to back, connected over SPI, would be able to transmit the keystrokes with minimal latency there. Course at that point, it's less hackish just to get one of the $10~$20 boards that has a usb input and output.