App to scan 4G networks

We are a company producing devices connected to our server with a 4G module. Before selling and installing the device we need to ensure that 4G connection signal is good. The need is to develop an app that should be able to scan all the available 4G networks, for each one get the available signal parameters and log them. The app must be able to automatically switch from one carrier to the next one. From a user experience point of view, we expect that user interaction will be minimal, just start the scan and have a report of all the available carriers with signal params. >>>> I want to stress this point. The application must be able to scan all the available networks and get signal strenght values for all. We already know this is not possible with a "normal" app, but it needs deep android knowledge. <<<< The app will be integrated in more complete app already in development. So we don't need too much effort on the interface, but we need to focus on the scan. Code should be primarly for Android, phone and/or tablet. If the app can run only on a specific Android version or specific phone (rooted?) we are ok, since the usage is only for our employee.