Gesture recognition using the onboard gyroscope and accelerometer (I think - it was 2 years ago!), and it took me some part of an afternoon.
I also used these two resources (the book was definitely useful; less sure if the arduino link the the same one I referred to then), which I found to be useful:
I also used these two resources (the book was definitely useful; less sure if the arduino link the the same one I referred to then), which I found to be useful:
[1] https://docs.arduino.cc/tutorials/nano-33-ble-sense/get-star...
[2] https://www.oreilly.com/library/view/tinyml/9781492052036/