You can tell your friends and family they should be shooting videos horizontally all you want, but that won't stop them from capturing unwieldily vertical clips that are impossible to fullscreen on a computer. But there's finally a solution to this problem. Simply hide their default camera app—bury it deep in a folder somewhere—and replace it with Horizon, a replacement camera app that captures horizontal videos no matter how the device is held.
Available for most newer iOS devices with a camera that can capture video, the app relies on your phone or tablet's built-in gyroscope to automatically keep a scene framed in a perfectly level 16:9 aspect ratio, even while it's being rotated.
The downside, of course, is that all the videos captured by the Horizon app will be limited in resolution. Where as the iPhone 5S can capture full 1920x1080 clips with its default app, Horizon would have to instead be limited to a resolution of 1080x608 when capturing a 16:9 video in a vertical orientation. But that's still much higher than standard definition, and for just a buck it guarantees your parents never share an awkward vertical video with you ever again. [Evil Window Dog via Ubergizmo]