Yes, the app stays active if the screen locks or if you switch to another app. The device will also continue with the treatment.
Does the Philips Treatment App run / continue on the background?
Stop running on background
However, in the app settings it is possible to stop running the treatment on the background via ‘Settings’ – ‘Run treatment in background’.
If you choose to stop running the treatment on the background, then the treatment in both the app and the device stops. This only happens if you go back to the main screen of your mobile device or if you switch to another app. If the screen locks automatically while the app is still open on your screen, the treatment will continue. If you unlock the screen then, you will see the app and treatment continued.