I recently learned the selfie camera thingy on my phone (Samsung A5) could be voice activated by the commands "capture", "smile", "cheese" and "shoot" with a 2 second timer.
I used this as an impromptu speaking test. If the students could get 3 of the four commands to work after trying each word three times, I'd give them a 50 point bonus on their literature task (normally it takes 300+ points to pass, with assignments usually worth ~20-30 points each).
It was a huge success and something fun to do as a filler activity.