Similar to the idea of the SoundWave gesture detection technique published in Microsoft Research, this game uses your device's speaker to generate an inaudible tone, and uses your device's microphone, along with the physics of the Doppler Effect, to detect your motion.
How It Works:
1) The program generates an inaudible 20 kHz tone from your device's speaker.
2) It uses your device's microphone to monitor the sound.
3) Using the mathematics of the Fourier Transform, it determines the spectrum of frequencies contributing to the measured sound.
4) When you move your hand toward the microphone, the 20 kHz frequency is shifted higher in accordance with the Doppler Effect, allowing the program to detect your hand motion.
How To Play:
Make sure your device's volume is on
Keep your device as still as possible for maximum accuracy
Move your hand toward your device's microphone to move the bird
Keep your hand still when you don't want the bird to move
Notes:
This has only been tested on a very limited number of devices at this point, so results may vary.
The network permission is for Google Play Games Services: leaderboards, achievements, etc.
The original SoundWave paper: http://research.microsoft.com/en-us/um/redmond/groups/cue/publications/guptasoundwavechi2012.pdf
More information about / implementations of this idea: https://github.com/DanielRapp/doppler