Rob, I hate to tell you this since it is going to seem so obvious but it is made by the Specialized Bicycle Components, Inc. It is a SpeedZone Model. I cannot find a website for them but they are located at 15130 Concord Circle, Morgan Hill, CA 95037.
To program the wheel size, do a rollout to determine your wheelsize in millimeters. To enter the tire circumference number, advance the computer to the ODO mode and press the left side function button for over four seconds. The last programmed number, or default 2124, will appear and one digit will begin to flash. Press the lower function button to select the correct digit. When the flashing digit is correct, press the left side funtional button. The next digit to be adjusted will begin to flash. Repeat the process for all four digits of your tire circumference. Press the left side funtion button and you will enter your programmable odometer function. You can enter you previous odometer reading here, or just press the left side function button until you exit this function.