Apple has added a handy feature into OS X to easily capture the screen of an iPad or iPhone on the Mac itself. Apple positions the feature as a way to help developers quickly make app previews, which Apple introduced as part of iOS 8’s improvements to the App Store, but there is no reason why this couldn’t be used by others for different purposes.
When plugging an iPad or iPhone running iOS 8 into a Mac running OS X Yosemite via USB, the iOS device now shows up as a standard camera input. This means any video app can be used to record the screen of the iOS device without the need for additional hardware.
Although Apple is targeting the feature at developers in its documentation for making app previews, it is not limited to being a developer-only feature.