Not this one, though. It's actually surprisingly expensive for what it is. One could build this with an ESP32 and a couple of jellybean parts to regulate the vo

Not this one, though. It's actually surprisingly expensive for what it is. One could build this with an ESP32 and a couple of jellybean parts to regulate the voltage to what the chip needs and create a voltage divider. Even with a case, it's less than $15 BOM. You'd have to write the phone app, but that would be as complex as you wanted.