AWS Device Farm - Improve the quality of your iOS, Android, and web applications by testing against real mobile devices in the AWS Cloud.
Maze - Beautiful & actionable analytics for InVision prototypes
Test Anywhere - A cloud service that helps test your website
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.
AppThwack - Test your app on 100s of real devices in the cloud.
W3C Mobile Checker - Make websites work better on mobile devices