Google earth has realtime
GPS tracking capabilities?!? How are you going to get wi-fi on your boat? Have they started putting depths on google earth sat photos? And listing nav aids and shipping channels?
Download free raster
charts from noaa and get an inexpensive plotting software for your laptop. You will still need at least an inexpensive
handheld gps and a usb cable for it but that's about as cheap as it gets.