Apple comes with a new feature in its OS X Yosemite. Do you need to take screencast from your mobile device? There was a few ways how to do it and now there is one directly from Apple.
All you need to do is to connect your iPad or iPhone to the Mac running the new OS X 10.10 Yosemite (which is currently in beta). Your device then become available as a standard camera input. After that you can use any screen recording / screencasting app on you Mac to take the video of the mobile device's screen.
Source: 9to5Mac