It’s pretty basic. I took a piece of cork and a string to attach it to the base of a mason jar, so the cork is suspended about halfway up, then I filled it with water. I just put that mounted to the center of my dash, and it indicates how much lateral force I’m using during turns. As long as I keep it as close to the center as possible, I’m using the smoothest line.
Fantastic!
I personally own an old pre-smartphone accelerometer with a built-in acceleration calculator (and what is now considered retro LED display) that pretty much works on the same principle, a free-moving arm is attached to a potentiometer to measure the angle accurately (though that only works in one direction).
The accelerometers we use for crash testing use two little crystals rubbing together, they can pick up changes as little as 0.1G but also remain accurate up to 2000G.
