There are doorknobs with microcontrollers in them, so how about nightlights? We had houseguests, it was late, and I needed an extra nightlight in a hurry. I had all kinds of glowy things from Adafruit, but I didn't want to wire anything up. The RGB LED on a Gemma M0 was bright enough, and all I had to do was supply power. In one minute, I had a nightlight. Later I made it fancier.