The Sun Sensor gives a near spacecraft or BalloonSat the capability to detect the sun's position related to the craft. Some experiments, cameras for instance, perform better when they don't point directly at the sun. By reading reports from the Sun Sensor, a flight computer can properly operate experiments based on the sloar quadrant.
The Sun Sensor kit costs $21.50 plus $4.00 S&H.
Assembly directions for the Sun Sensor kit
Sun Sensor Code
To program the GPS Simulator's PICAXE-14M2, you'll need to download the PICAXE Programmer. It's free at this link