[mywittyname]

I remember having an assignment like this my second year of college. It was basically an array of various smoke detector sensors wired up to a parallel port. With diverse enough sensors, you could stick a cup into a box with a fan and the sensor, and be able to tell if the cup had OJ, coke, or coffee in it using basic PCA.

Given the tools available now, I'm not surprised a smart 13yo could build something like this. Especially if the sensor itself is an off-the-shelf component with device drivers and such already available for it.