I like the button idea. 1. I'd love to see it battery powered. 2. I found a vape thing yesterday - I would love to see a battery from a Vape re-used if possible. 3. Lastly - based on a project I'm trying to do now. Can you somehow sleep the microcontroller so it uses no power while in standby and then starts the timer, so you have close to indefinite battery life?

I get the diy factor, but still, the smartphone was supposed to be smart...

But, I thought Arduino had become officially evil once it joined Qualcomm. Besides which a Raspberry Pi Pico is cheaper than any Arduino-branded board ever was. So I'd just program this type of thing in MicroPython.

I do see that in the article, the project used an Adafruit Trinket M0, a very cute little board that has CircuitPython already installed. So I wonder why not just use CircuitPython. Anyway though, it's a Cortex M0 board, rather than the traditional Atmega that the Arduino world grew up using.