I used a MAX7456 chip in combination with the Ardupilot Mega to put info on screen. It's relatively easy to use. You need some time for developing the characters. The easiest way is to get the zip package with the utilities for the chip and then load the chardata through a serial tunnel on the arduino.
The chip is capable of doing numbers and logo's and all kinds of icons. It's not a good chip for line drawing though or vertically placed text.