4G SIM-based Security Camera Prototype

I am looking for an experienced electronics/IoT developer to build a **working prototype of a 4G SIM-based security camera and a simple mobile app**.

The camera should work without Wi-Fi and connect to the internet using a SIM/4G network.

### Prototype Requirements

* Camera with live video
* 4G/SIM connectivity
* Microphone + speaker for two-way communication
* Battery powered
* USB-C/external power or power bank support
* Remote viewing from a mobile app
* Basic camera controls
* Simple backend/cloud connection
* Prototype should support the concept of having multiple cameras at one location

For the first stage, I am **not looking for a production-ready/custom-manufactured camera**. Commercially available development boards/modules can be used.

The goal is to build **one complete working prototype** and demonstrate that the camera can be remotely accessed and controlled through the app over 4G or 5G

Please mention:

1. Your experience with 4G/LTE camera or IoT projects.
2. Similar projects you have completed.
3. Hardware/platform you would recommend for the prototype.
4. Estimated time and cost for the prototype.

Source code, firmware and project files should be handed over at completion.