Contact person: Incoming Call Alerts via FCM

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Location: Reading, United Kingdom

Budget: Recommended by industry experts

Time to start: As soon as possible

Project description:
"I need help wiring Firebase Cloud Messaging into my mobile app so that users see a real-time alert whenever an incoming call arrives. The single goal is to raise a full-screen “ringing” interface the moment my server flags a new call, even if the app is killed or in the background.

Here’s the flow I have in mind: the backend sends a data-only FCM payload with the caller’s details; the device receives it, wakes up, and presents the native call UI (CallKit on iOS, a ringing activity/service on Android). You’ll also make sure the notification channel, sound, vibration and action buttons behave exactly like the system phone app. I’ll handle the actual VoIP connection once the user presses “accept”—your job stops right after the alert hands control over to the existing call screen.

Please set up:
• Server-side sample showing the JSON payload I should send through FCM
• Client-side code (Swift for iOS, Kotlin or Java for Android) that registers the device, listens for the push, and triggers the call UI even on a cold start
• Clear instructions on any Apple VoIP entitlement or background mode settings, plus the required notification channel configuration on Android

The implementation must be lightweight, respect battery limits, and follow current Firebase and platform guidelines. Let me know how quickly you can turn around a working proof of concept and your preferred approach so we can lock in milestones right away." (client-provided description)