One Click Test - Tool for quickly testing your design layout in one click.
Maze - Beautiful & actionable analytics for InVision prototypes
W3C Mobile Checker - Make websites work better on mobile devices
UXCam - UXCam is the market leader for qualitative app analytics. UXCam provides instant insight into customer behavior in the app through deep analysis of user sessions, events, screen flows, heatmaps, and interactions.
Flexbox Grid - Grid based on CSS3 flexbox
Koncept - Usability testing, interactive prototypes & metrics