Android: Swipe up from the bottom of your handset's screen, and Google Now springs into action. Swipeup Utility lets you use the same gesture to start a different app, if you prefer.
If you don't use Google Now, you can disable it completely by flicking the Google Now switch to Off in its settings. Either way, that swipe gesture is pretty handy.
To change the gesture, download a copy of Swipeup Utility from the Google Play store. The app disables the upward swipe gesture entirely, but you can also use it to create a shortcut of your own. Install and launch the app, and then open up the settings.
To simply disable the swipe gesture, you don't need to do anything -- Swipeup Utility takes care of this for you. If you would like to use the upward swipe gesture to launch a different app, tap "Choose action" in the Gesture section of the app. Select an app or action from the list and enjoy easy access from this point forward.