Watt: That blue thing is your mom! oooohh burn! Wait... That doesn't even make any sense. No, it's a LEM current sensor:
Digi-Key - 398-1065-ND (LEM USA Inc - HASS 300-S)
It lets you know how much current is going through at any given time. It's nice for things like controlling throttle based on current. It's also how I know when an overcurrent event has happened, so that the hardware shuts off the mosfet driver until the software re-enables it.
Denmark: The controller will get drug testing. hehe. No! Just kidding, Denmark! It will be tested in Romania. High temperature testing (40 degC, whatever that is), and I'm not sure what else. Wait! It's also a test of the concept of the kit! Can it be assembled with the help of my crappy directions?