Hey PieLover.. Yes as said above you could.. But perhaps these projects which use similar Off the shelf BLE sensors might give you a clearer picture of just how a Pi could be used very easily with little effort beyond a bit of cut and paste at the cli to interface with such devices and use the sensor input for display, logging, or even as the input to further processing to derive further output or actions..
https://zsiti.eu/xiaomi-mijia-hygrother ... pberry-pi/
While phone apps seem useful they frequently demand excessive privileges over data and h/w in your device And a Pi makes an ideal substitute to run only the code YOU WANT to execute in response to any sensor readings you may take. And It hardly makes sense that your phone needs to handshake with servers in china? just so you can read the sensor that is 3 feet from you when you set it up..
Instead of a Phone app you host either a webpage or a dashboard on the pi which you can use your phone or any browser enabled device to connect and open to display your data and controls.
If using mqtt as in both examples above Node Red provides a very quick method to develop a dashboard interface for any controls and displays of data.
While Mammoth Projects can develop interesting and useful results, its best to stick with stuff you can accomplish most of if not all on a sunday afternoon when starting out