Samsung has this too (not sure about other Androids), it's called "pin app". It also makes the app come up immediately when your turn on the screen, so it's in

Samsung has this too (not sure about other Androids), it's called "pin app". It also makes the app come up immediately when your turn on the screen, so it's in front of the lock screen basically (but you can only access that particular app). It's good for showing someone a specific app. I also use it for instant access to my train ticket (QR code on screen on the train company's app). The iOS version sounds better though.