I built one! Arduino Leonardo and a light dependent transistor: https://github.com/willmuldrew/lagmeter https://github.com/willmuldrew/lagmeter (It attempts t

I built one! Arduino Leonardo and a light dependent transistor: https://github.com/willmuldrew/lagmeter https://github.com/willmuldrew/lagmeter (It attempts to do a few other things but it’s best for measuring keyboard event to screen update latency)