Once you start buying easy-to-program microcontroller gadgets from Crowd Supply and Adafruit Industries, it is hard to stop. Nowadays they all have bluetooth bu

Once you start buying easy-to-program microcontroller gadgets from Crowd Supply and Adafruit Industries, it is hard to stop. Nowadays they all have bluetooth built in, so can be controlled wholly from your phone; no buttons, display, or even USB connector needed.