Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Instabug - The top apps in the world rely on Instabug for beta testing, user engagement and crash reporting.
Mockup Generator - Create attractive product screenshots with just a few clicks
UserTest.io - User testing made simple. High-quality, affordable user testing solutions from real users, here in the UK. Improve your usability!
shotsnapp - Create beautiful device mockup presentation
UserTesting.com - Usability testing has never been easier. Get videos of real people speaking their thoughts as they use websites, mobile apps, prototypes and more!