The board most likely consists of an array of proximity detectors and LEDs. This can be achieved using a pair of wavelength matched phototransistor and LED for the detector, a visible LED, and a bunch of relevant resistors. Ideally, the phototransistor-LED pair should utilise non-visible radiation, near IR is most common. I decided to try my hand at designing a through-hole pcb instead of using perfboard as usual. This should be relatively simple even for a novice at Cadsoft Eagle like myself.
It should be simple right?