Sketch Mirror - Preview your iOS designs directly on your devices

TestFlight - iOS beta testing on the fly.

Crystal: Sketch Mirror for Android - Crystal: Sketch Mirror for Android is an application that is designed for viewing your sketch designs in real-time, navigate prototypes and download content related to the sketches for offline viewing.

TestFairy - Painless Beta Testing

Figma Mirror - Figma Mirror is an application that covers top trending designing or sketching ideas making your teamwork in a single environment and design better products from start to finish.

TestApp.io - A platform that helps both mobile app developers and owners to easily share their apps with everyone to get feedback before reaching publicly to Google and App stores.