Visual effects like parallax have been around since the 1980s and have been popularized as a development technique during the golden days of gaming in the 16 bit era. Parallax effects simulate depth by giving the foreground and background layers of an interface independent constraints in direction. An example of this is when you play Super Mario and the background seamlessly moves in reverse as you walk forward. The result is a multi-plane effect that makes for an illusion of depth.
Reverse wallpaper scrolling makes for a subtle but interesting experience on your phone. Android has had this capability for awhile (thanks to live wallpapers and custom launchers that are easily obtainable) but thanks to the introduction of iOS7 a whole new user base is starting to get exposed.
Several launchers and base ROMs already have included tweaks like wallpaper scrolling, but one of the best apps we've seen is 3D Image Live Wallpaper. 3D Image Live Wallpaper is wallpaper app for Android that lets you use custom images that pan and tilt based on your phone's built in gyroscope data. The results a window-like effect that breathes new life into your desktop and app drawers.
3D Parallax Background is another app that produces similar effects and also gives you the option of isolating your sensors to strictly only using the accelerometer, as opposed to the gyroscope. It's about half a buck cheaper, but overall we found performance to be much more desirable with the gyroscope-powered effects. However, it does come with some nifty multi-layered wallpapers that's sure to impress your friends or keep you visually entertained for a bit.