Anima App - Design, get feedback, convert to code, publish, iterate.
One Click Test - Tool for quickly testing your design layout in one click.
Sketch Repo - Collection of resources for anyone who uses Sketch
W3C Mobile Checker - Make websites work better on mobile devices
Auto-Layout for Sketch - Responsive design for Sketch
ProtoPie - ProtoPie is the easiest tool used to turn your UI/UX design ideas into highly interactive prototypes for mobile, desktop, web, all the way to IoT.