I was thinking about this this morning. A simple nav system made of an Arduino, GPS board, 16x2 LCD display, and rotary encoder knob. You enter the coordinates of your destination and it tells you the bearing. Can't get much simpler. Of course, I am already seeing some feature creap. Like the distance and your course. The simple version would only require simple trig. No great circle calculations etc. There are all kinds of Arduino nav systems on the internet, but they all seem to be moving map displays.