Take a look at this clever animatronic piece by Philip Lowndes. Though the piece is titled "Thumbs-up" that doesn't mean you will always get that sign. In fact, it is a capable of making random "yes" or "no" decisions based on its programming. The machine is equipped with a sensor that detects when a hand is waved in front of it, which sets it in motion.
From the artist's web site:
Animatronic moody decision making machine that makes decisions without bias, conflicts of interest, lobbying. No need for any background or relevant information. Just stand in front of the machine and it will give you its decisions. Useful for checking dress sense, purchase and investment decisions (at your own risk), strategies to save the Euro etc.
The piece is constructed from wood, nylon and brass. Toward the end of the video you can see the profile of some lovely wooden gears. The entire system is controlled by an Arduino microcontroller.
The mood of the machine can be changed to suit your needs by adjusting a knob on the front. Blue is a bad mood, green neutral, and yellow good.
Here is where you can learn more about the Thumbs-up Animatronic Decsion-Maker.