SOS Buzzer App for Android/iOS

I need a lightweight SOS application for both Android and iOS that can be launched with one clear purpose: when a user presses the dedicated on-screen button, a deafening buzzer must sound at maximum volume to draw attention and at the same moment prompt the user to send help alerts.

Core flow
• The user presses the SOS button (the only trigger for now).
• The app fires the loud buzzer instantly.
• A screen appears letting the user pick one of four pre-written messages and one of three pre-saved locations.
• The chosen combination is then dispatched to the user’s selected emergency contacts through the phone’s native sharing options (SMS, WhatsApp, etc., whichever is installed).

Configuration inside the app
• Settings page where the user manually stores the three fixed addresses (typed text, no map input).
• Separate settings screen to edit the four preset messages.
• Simple contacts selector so the user can add or remove recipients at any time.

Key requirements
• Works on current Android and iOS versions with identical behaviour.
• Buzzer must override the device’s volume setting and keep sounding until the user stops it or the alert is fully sent.
• All contact, address and message data remain strictly on the device—no external server needed.

Deliverable
A fully functional, store-ready mobile app package for both platforms, complete with commented source code and a short setup guide so I can rebuild or expand it later.

If everything above is clear and feasible for you, let’s get started.