Playing a lot of sports growing up I took a lot of hits. Thinking about it last year playing rugby, I wish I had something that could measure the force of hits, and a few other body vitals (temp, sweat, etc..).
Having just receive an arduino I started hooking up sensors and leds. I deiced to mount them in a hockey helmet.
This early prototype measured force with FSR’s inside the helmet, an accelerometer on the top, and temperature sensor.