You can control your media applications like Spotify and VLC Player with ControlAir. It uses your webcam to do do gestures with your finger.
Free • Proprietary
What is ControlAir?
ControlAir provides magical touch free control over media applications on your Mac, such as iTunes, Spotify and others. Just raise your finger in the air to control volume, skip songs and pause. A finger raised to your lips will mute the sound.
ControlAir is a great way to control your media applications touch-free, not only when they are in front of you, but also when they are in the background, while you are engaged with a different app.
To enjoy the touch-free control, you should face the camera of your device between 1 to 5 feet.
ControlAir supports the following apps: - iTunes - QuickTime Player - Rdio - Spotify - VLC - VOX - Gear for Google Play and YouTube
# Troubleshoot #
If you raise your finger and you don't see the control menu shows up, then it is probably because your finger is not visible. Open the Preferences window and then the Setup tab, and choose the 2nd section called Camera alignment, in it make sure that when you raise your finger it shows entirely in the view.