For a long time when I’ve wanted to test the latency of computers and UIs I’ve used the Is It Snappy app with my iPhone’s high speed camera to count frames between when I press a key and when the screen changes. However the problem with that is it takes a while to find the exact frames you want, which is annoying when doing a bunch of testing. It also makes it difficult to find out what the variability of latency is like. I had already made this kind of testing easier by adding a mode to my keyb...