Android: BrainWave controls your favourite music player app and controls it with the wave of a hand. Just select your music player and use the three gesture options to control it.
Hold your open palm above the app to play a song. Swipe left and right to skip forward, back or return to the beginning of a song. You can use it with a sleeping screen as well. The app is extra convenient for when you get your hands dirty, or when you're busy working and don't want to pick up your phone to switch songs.
It worked well when I tried it, but it's not perfect. Sometimes, it doesn't catch my gestures. If you do pick up your phone it may register false gestures, but that should be expected. The video above shows you how to use it. Grab the app below.