Timo Voutilainen started a new project. He connected a GPS device to the Commodore 64. If you want to build your own C64 navigation system you will need the following components: CRIUS NEO-6 GPS v3.0 + I2C-GPS NAV -combo, 3.3V USB FTDI cable, Arduino IDE 1.05 and a user-port connector.
Website: https://sites.google.com/site/dividedbit/home/c64-projects/gps-view