embedded systemsthings you can kick!
programmable keyboard-like user response device with sub-millisecond accuracy
A graduate student needed something with 4 "normal" buttons and a "home" button with sub-millisecond timing resolution. The "home" button is my favorite part. It is a screw head attached to a capacitive-sensing pin on a Teensy LC, with a library to make it behave like a pushbutton switch (source).
measures and records skin conductance levels
Myself and another engineer built 30 of these for an honors-level Psychology course at Indiana University. The device records skin conductance between 2 electrodes and logs the data to a micro SD card. Students devised their own experiments around the device, and presented their results at the end of the course. Experiment topics ranged from "watch a scary movie" to "listen to your favorite music".