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.