The creator of this is also the person behind Phyphox, an app that turns your smartphone into tool to conduct physics experiments with and collect data from them, creator of a Game Boy WiFi cartridge and GB Interceptor that allows to record videos of Game Boy games - among other things. Amazing what some people do, isn't it?
Phyphox is such a cool tool. The acceleration spectrogram is so cool to look at - you can put your phone top of your PC/laptop and measure the RPM of fans and spinning drives.
Agreed, thank you and the parent comment here for the mention of it - looks great, works great with the little bit of experimentation I've done so far.