EDIT: As of September 2020, it is now possible to log in to MATLAB Online and MATLAB Mobile simultaneously. Once you're signed in to the app with your MathWorks Account, you can also log in to MATLAB Online with the same account and use the MOBILEDEVLIST function to start connecting to your mobile device, as shown below:
It is currently not possible to MATLAB Online and MATLAB Mobile simultaneously.
One option: you can collect sensor data from MATLAB Mobile on your phone even when you are offline (i.e,. not connected to MathWorks Cloud) and later upload it to MATLAB Drive. I don't think it's still real-time, but perhaps an improvement over your current workflow.