It is, technically, possible to use multiple apps on the same smart device at the same time to control your drone. The majority of apps lock down their connection to the remote, lock to the USB interface of your phone or tablet, as a safety feature to prevent multiple simultaneous app actions, but it is otherwise quite possible to do. In the case of the Fluidity app, for example, we can easily jump back and forth between it and DJI GO 4 on the fly.