2.) It's the only thing that can help you when your batteries run out or the electronic computer stops working - I can buy an additional battery, I can buy two electronic computers. I've never had an electronic handheld device fail on me. Ever.
I have had 1 wiz wheel melt on the dash, and have had 1 GPS handheld zap itself in the middle of the NT (And out came the map from the back of the seat).
Dont put to much trust in your little handheld device, electric or otherwise.