kai-wu-cortex / AirSIM

Source-available, noncommercial cross-device calling and messaging for Samsung Android, iPhone, Apple Watch, AVF Linux and Cloudflare Workers.

OneSignal / OneSignal-Android-SDK

OneSignal makes engaging customers simple and is the fastest, most reliable service to send push notifications, in-app messages, SMS, and emails. This plugin makes it easy to integrate your native Android or Amazon app with OneSignal. https://onesignal.com