Design a mobile app for both IOS & Android devices for a bluetooth activity tracker watch

We need an app design and built for both IOS and Android. We have a Bluetooth activity tracker watch which counts steps, monitors heart rate, blood pressure, oxygen saturation and monitors sleep, it sends this information to the phone where it is displayed in graphs to monitor activity over time. There is already an app that works with the watch, however, I would like one build our own based to a large degree on the existing app but with some changes. We are able to get the SDK from the manufacturer of the watch, there are a total of two models that we would need to work with the app, we would provide the SDK for both. We have designed all the artwork for the app and will provide this in a Vector format to the company that designs the app. We would expect the company that builds the app to make minor changes to the artwork design, buttons, selection tabs ect if needed. The graphs would be interactive so that when one of the graphs is clicked on, the data that it represents will be shown by a number on top of that graph. Whoever builds out app would also need to create a database system so that when we sell the watch, we would enter the watch number into this database. When a customer registers the device (on the main setup screen), they will need to enter the number that came with the device, this would allow them to use the app and the database would have a record of their username and password along with the number that they originally registered. If they change phones, they would need to enter their username and password so that they can use the app. We would require a cost for the ongoing database use. I have attached a flowchart showing the artwork we have and what we require. In addition to this, we have the logo, splash screen and settings page that we will supply once the job has been assigned.