How can I "tilt to zoom"?

Tap on the mode button (top left button while holding your device vertically) to select "Flex" mode.

Flex, intelligently adjusts the zooming scale to provide a smooth recording. So, if you hold your device vertically it will zoom in. While you are tilting your device to a horizontal position, it will zoom out. You can even try to rotate it with higher speeds for a cool effect.