Fluid for Sketch - Sketch plugin to make your responsive designs more efficient
Device Shots - Generate high-resolution device mockups using a screenshot.
Anima App - Design, get feedback, convert to code, publish, iterate.
Facebook Design - Devices - Images and Sketch files of popular devices.
Git Sketch Plugin - Version control for designers
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.