Mobile App Engagement platforms power push notifications, in-app messages, and mobile-engagement workflows for companies with mobile apps. The category serves a different buyer than SMS & Messaging — Mobile Marketing Manager / Mobile Product Manager — with different metrics (DAU/MAU/retention, app-store policies, push-token management) and different infrastructure (iOS/Android SDKs, OS-level notification delivery). Core capabilities include push notification campaigns with personalization, in-app message overlays, push-token lifecycle management, app onboarding flows, behavior-triggered push, A/B testing, and deep-linking from notifications to app content. The market spans mobile-first engagement platforms (OneSignal, Airship, Leanplum) and push-notification specialists (Pushwoosh, PushEngage).