Raspberry Pi Serial TTY Console
From KlavoWiki
Using a PL2303HXD cable connect to a USB port on the computer. I bought mine form eBay for around AU$6. Make sure you get the PL2303HXD and not the PL2303HX. Note the D on the end of the model number.
sudo wget https://raw.githubusercontent.com/lurch/rpi-serial-console/master/rpi-serial-console -O /usr/bin/rpi-serial-console sudo chmod +x /usr/bin/rpi-serial-console
rpi-serial-console <status|enable|disable>