Apple and Android phones already come with a feature that allows the user to keep an app active on the screen and prevents the user from accidentally turning off the app or switching to another app. Apple calls this feature “Guided Access”, and Android calls this feature “pin an app.”

To enable Guided Access on iPhone, follow these steps:

1. Open the "Settings" app on your iPhone.
2. Go to "Accessibility."
3. Tap on "Guided Access" (under the "Learning" section).
4. Toggle the switch to enable Guided Access.
5. Set a passcode that will be required to exit Guided Access.
6. Open the app you want to restrict access to.
7. Triple-click the side button (on iPhone X and newer) or the Home button (on iPhone SE, iPhone 8 and older).
8. Tap on "Start" to activate Guided Access.

To exit Guided Access, triple-click the side or Home button (depending on your iPhone model) and enter the passcode you set.

To pin an app on Android, follow these steps:

1. Open the "Settings" app on your Android device.
2. Navigate to "Security" or "Lock screen and security" (the exact path may vary depending on your device).
3. On Samsung you will need to navigate to "Other Security Settings"
4. Look for and tap on the "Screen pinning" or "Pin screen" option.
5. Enable the feature by toggling the switch.
6. Open the app you want to pin or restrict access to.
7. Swipe up or tap the square overview button (the recent apps button) to view the list of running apps
8. On Samsung press the app icon located above the app
9. You may be prompted to set a lock screen PIN or pattern if you haven't already.
10. The app will now be pinned to the screen, and users won't be able to switch to other apps without first unpinning it.

To unpin the app, press and hold the back and overview buttons simultaneously until the app is unpinned, or if using swipe controls swipe up and hold.