Finally, a decent solution for recording video from iPhone, one that is both perfect and free. Apple has an awesome (yet hidden) feature with Yosemite + iOS 8: QuickTime recording via your Lightening cable.
Follow the steps (copied below after the jump). You can also use it to present an iOS demo (follow the steps, but don’t tap ‘record’, and then present/cast your screen in the usual way). They even set the clock to 9:41 ;-)
For App Previews, to edit and crop the video, use iMovie, (File -> “New App Preview”, File -> Share -> App Preview…). While quicktime has edit controls, it can’t export at the resolution needed.
To resize for iPhone 6 Plus (and avoid making another video), use ffmpeg:
ffmpeg -i iphone6.mp4 -s 1080x1920 -aspect 1080:1920 -c:a copy iphone6_plus.mp4
(Lightning port ONLY)
File > New Movie Recording