Running the
navigation system off a raspberry pi makes redundancy
cheap and easy. The pi
power supply and sd card is less than $50 and can be down in the
boat in a controlled
environment. The ipad can be less than a few hundred dollars. Redundancy on the viewing screen (ipad) can be anything that will run VNC. I've run it on my
Iphone, Ipad, Android, tablet, Macbook, Windows
laptop. You get my point. This setup opens up a lot of redundancy and flexibility. The Pi and Openplotter/Opencpn opens up a lot of expansion with the 40 GPIO pins, 4 usb
ports, and wifi connectivity for sensors, AIS overlay, and
NMEA bus. I tend to use my Ipad as a navigation
remote screen and a Ereader at the same time. Sometimes use my
Iphone for a nav screen and run a
movie on the ipad or visa versa at night.